<?xml version="1.0" encoding="US-ASCII" standalone="no"?>
    <!-- Field: Doc-Info; Name: Generator; Value: GoFiler Complete; Version: 5.3c -->
    <!-- Field: Doc-Info; Name: VendorURI; Value: http://www.novaworks.co -->
    <!-- Field: Doc-Info; Name: Source; Value: OPTT %2D 20200430 10K FY DFN.xfr; Date: 2020%2D06%2D29T10:58:05Z -->
    <!-- Field: Doc-Info; Name: Status; Value: 0x802F0000 -->
<link:linkbase xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xbrli="http://www.xbrl.org/2003/instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/DocumentAndEntityInformation" xlink:href="optt-20200430.xsd#DocumentAndEntityInformation" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/BalanceSheets" xlink:href="optt-20200430.xsd#BalanceSheets" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/BalanceSheetsParenthetical" xlink:href="optt-20200430.xsd#BalanceSheetsParenthetical" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/StatementsOfOperations" xlink:href="optt-20200430.xsd#StatementsOfOperations" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/StatementsOfComprehensiveLoss" xlink:href="optt-20200430.xsd#StatementsOfComprehensiveLoss" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/StatementsOfStockholdersEquity" xlink:href="optt-20200430.xsd#StatementsOfStockholdersEquity" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/StatementsOfCashFlows" xlink:href="optt-20200430.xsd#StatementsOfCashFlows" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/BackgroundAndLiquidity" xlink:href="optt-20200430.xsd#BackgroundAndLiquidity" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/SummaryOfSignificantAccountingPolicies" xlink:href="optt-20200430.xsd#SummaryOfSignificantAccountingPolicies" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/AccountReceivableContractAssetsAndContractLiabilities" xlink:href="optt-20200430.xsd#AccountReceivableContractAssetsAndContractLiabilities" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/OtherCurrentAssets" xlink:href="optt-20200430.xsd#OtherCurrentAssets" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/PropertyAndEquipment" xlink:href="optt-20200430.xsd#PropertyAndEquipment" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/Leases" xlink:href="optt-20200430.xsd#Leases" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/AccruedExpenses" xlink:href="optt-20200430.xsd#AccruedExpenses" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/Warrants" xlink:href="optt-20200430.xsd#Warrants" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/PreferredStock" xlink:href="optt-20200430.xsd#PreferredStock" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/CommonStock" xlink:href="optt-20200430.xsd#CommonStock" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/TreasuryShares" xlink:href="optt-20200430.xsd#TreasuryShares" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/Share-basedCompensationPlans" xlink:href="optt-20200430.xsd#Share-basedCompensationPlans" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/FairValueMeasurements" xlink:href="optt-20200430.xsd#FairValueMeasurements" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/IncomeTaxes" xlink:href="optt-20200430.xsd#IncomeTaxes" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/CommitmentsAndContingencies" xlink:href="optt-20200430.xsd#CommitmentsAndContingencies" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/OperatingSegmentsAndGeographicInformation" xlink:href="optt-20200430.xsd#OperatingSegmentsAndGeographicInformation" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/SubsequentEvent" xlink:href="optt-20200430.xsd#SubsequentEvent" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/SummaryOfSignificantAccountingPoliciesPolicies" xlink:href="optt-20200430.xsd#SummaryOfSignificantAccountingPoliciesPolicies" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/SummaryOfSignificantAccountingPoliciesTables" xlink:href="optt-20200430.xsd#SummaryOfSignificantAccountingPoliciesTables" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/AccountReceivableContractAssetsAndContractLiabilitiesTables" xlink:href="optt-20200430.xsd#AccountReceivableContractAssetsAndContractLiabilitiesTables" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/OtherCurrentAssetsTables" xlink:href="optt-20200430.xsd#OtherCurrentAssetsTables" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/PropertyAndEquipmentTables" xlink:href="optt-20200430.xsd#PropertyAndEquipmentTables" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/LeasesTables" xlink:href="optt-20200430.xsd#LeasesTables" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/AccruedExpensesTables" xlink:href="optt-20200430.xsd#AccruedExpensesTables" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/WarrantsTables" xlink:href="optt-20200430.xsd#WarrantsTables" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/Stock-basedCompensationTables" xlink:href="optt-20200430.xsd#Stock-basedCompensationTables" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/FairValueMeasurementsTables" xlink:href="optt-20200430.xsd#FairValueMeasurementsTables" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/IncomeTaxesTables" xlink:href="optt-20200430.xsd#IncomeTaxesTables" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/OperatingSegmentsAndGeographicInformationTables" xlink:href="optt-20200430.xsd#OperatingSegmentsAndGeographicInformationTables" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/BackgroundAndLiquidityDetailsNarrative" xlink:href="optt-20200430.xsd#BackgroundAndLiquidityDetailsNarrative" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/SummaryOfSignificantAccountingPoliciesDetailsNarrative" xlink:href="optt-20200430.xsd#SummaryOfSignificantAccountingPoliciesDetailsNarrative" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/SummaryOfSignificantAccountingPolicies-ScheduleOfCashAndCashEquivalentsDetails" xlink:href="optt-20200430.xsd#SummaryOfSignificantAccountingPolicies-ScheduleOfCashAndCashEquivalentsDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/SummaryOfSignificantAccountingPolicies-ScheduleOfCashAndCashEquivalentsAndRestrictedCashDetails" xlink:href="optt-20200430.xsd#SummaryOfSignificantAccountingPolicies-ScheduleOfCashAndCashEquivalentsAndRestrictedCashDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/SummaryOfSignificantAccountingPolicies-ScheduleOfPropertyPlantAndEquipmentUsefulLifeDetails" xlink:href="optt-20200430.xsd#SummaryOfSignificantAccountingPolicies-ScheduleOfPropertyPlantAndEquipmentUsefulLifeDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/SummaryOfSignificantAccountingPolicies-ScheduleOfRevenueByMajorCustomersByReportingSegmentsDetails" xlink:href="optt-20200430.xsd#SummaryOfSignificantAccountingPolicies-ScheduleOfRevenueByMajorCustomersByReportingSegmentsDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/SummaryOfSignificantAccountingPolicies-ScheduleOfEmployeeServiceShare-basedCompensationAllocationOfRecognizedPeriodCostsDetails" xlink:href="optt-20200430.xsd#SummaryOfSignificantAccountingPolicies-ScheduleOfEmployeeServiceShare-basedCompensationAllocationOfRecognizedPeriodCostsDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/AccountReceivableContractAssetsAndContractLiabilities-ScheduleOfAccountsReceivableDetails" xlink:href="optt-20200430.xsd#AccountReceivableContractAssetsAndContractLiabilities-ScheduleOfAccountsReceivableDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/OtherCurrentAssets-ScheduleOfOtherCurrentAssetsDetails" xlink:href="optt-20200430.xsd#OtherCurrentAssets-ScheduleOfOtherCurrentAssetsDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/PropertyAndEquipmentDetailsNarrative" xlink:href="optt-20200430.xsd#PropertyAndEquipmentDetailsNarrative" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/PropertyAndEquipment-ScheduleOfComponentsOfPropertyAndEquipmentNetDetails" xlink:href="optt-20200430.xsd#PropertyAndEquipment-ScheduleOfComponentsOfPropertyAndEquipmentNetDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/LeasesDetailsNarrative" xlink:href="optt-20200430.xsd#LeasesDetailsNarrative" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/Leases-ScheduleOfRight-ofUseAssetsAndLeaseLiabilitiesDetails" xlink:href="optt-20200430.xsd#Leases-ScheduleOfRight-ofUseAssetsAndLeaseLiabilitiesDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/Leases-ScheduleOfRemainingLeasePaymentsUnderOperatingLeaseDetails" xlink:href="optt-20200430.xsd#Leases-ScheduleOfRemainingLeasePaymentsUnderOperatingLeaseDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/Leases-ScheduleOfFutureMinimumLeasePaymentsUnderOperatingLeaseDetails" xlink:href="optt-20200430.xsd#Leases-ScheduleOfFutureMinimumLeasePaymentsUnderOperatingLeaseDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/AccruedExpenses-ScheduleOfAccruedExpensesDetails" xlink:href="optt-20200430.xsd#AccruedExpenses-ScheduleOfAccruedExpensesDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/WarrantsDetailsNarrative" xlink:href="optt-20200430.xsd#WarrantsDetailsNarrative" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/Warrants-ScheduleOfFairValueAssumptionsUsedDetails" xlink:href="optt-20200430.xsd#Warrants-ScheduleOfFairValueAssumptionsUsedDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/PreferredStockDetailsNarrative" xlink:href="optt-20200430.xsd#PreferredStockDetailsNarrative" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/CommonStockDetailsNarrative" xlink:href="optt-20200430.xsd#CommonStockDetailsNarrative" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/TreasurySharesDetailsNarrative" xlink:href="optt-20200430.xsd#TreasurySharesDetailsNarrative" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/Share-basedCompensationDetailsNarrative" xlink:href="optt-20200430.xsd#Share-basedCompensationDetailsNarrative" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/Share-basedCompensationPlans-ScheduleOfShare-basedPaymentAwardStockOptionsValuationAssumptionsDetails" xlink:href="optt-20200430.xsd#Share-basedCompensationPlans-ScheduleOfShare-basedPaymentAwardStockOptionsValuationAssumptionsDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/Share-basedCompensationPlans-ScheduleOfStockOptionActivityDetails" xlink:href="optt-20200430.xsd#Share-basedCompensationPlans-ScheduleOfStockOptionActivityDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/Share-basedCompensationPlans-ScheduleOfNon-vestedRestrictedStockActivityDetails" xlink:href="optt-20200430.xsd#Share-basedCompensationPlans-ScheduleOfNon-vestedRestrictedStockActivityDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/FairValueMeasurements-ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisDetails" xlink:href="optt-20200430.xsd#FairValueMeasurements-ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/FairValueMeasurements-SummaryOfChangesOnValueOfWarrantLiabilityUsingSignificantUnobservableInputsDetails" xlink:href="optt-20200430.xsd#FairValueMeasurements-SummaryOfChangesOnValueOfWarrantLiabilityUsingSignificantUnobservableInputsDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/IncomeTaxesDetailsNarrative" xlink:href="optt-20200430.xsd#IncomeTaxesDetailsNarrative" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/IncomeTaxes-ScheduleOfComponentsOfLossBeforeIncomeTaxesDetails" xlink:href="optt-20200430.xsd#IncomeTaxes-ScheduleOfComponentsOfLossBeforeIncomeTaxesDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/IncomeTaxes-ScheduleOfEffectiveIncomeTaxRateReconciliationDetails" xlink:href="optt-20200430.xsd#IncomeTaxes-ScheduleOfEffectiveIncomeTaxRateReconciliationDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/IncomeTaxes-ScheduleOfDeferredTaxAssetsAndLiabilitiesDetails" xlink:href="optt-20200430.xsd#IncomeTaxes-ScheduleOfDeferredTaxAssetsAndLiabilitiesDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/CommitmentsAndContingenciesDetailsNarrative" xlink:href="optt-20200430.xsd#CommitmentsAndContingenciesDetailsNarrative" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/OperatingSegmentsAndGeographicInformationDetailsNarrative" xlink:href="optt-20200430.xsd#OperatingSegmentsAndGeographicInformationDetailsNarrative" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/OperatingSegmentsAndGeographicInformation-ScheduleOfRevenueFromExternalCustomersAndLong-livedAssetsByGeographicalAreasDetails" xlink:href="optt-20200430.xsd#OperatingSegmentsAndGeographicInformation-ScheduleOfRevenueFromExternalCustomersAndLong-livedAssetsByGeographicalAreasDetails" xlink:type="simple" />
    <link:roleRef roleURI="http://oceanpowertechnologies.com/role/SubsequentEventDetailsNarrative" xlink:href="optt-20200430.xsd#SubsequentEventDetailsNarrative" xlink:type="simple" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/DocumentAndEntityInformation" xlink:title="00000001 - Document - Document and Entity Information" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/BalanceSheets" xlink:title="00000002 - Statement - Consolidated Balance Sheets">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetsCurrent" xlink:label="loc_us-gaapAssetsCurrent" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaapCashAndCashEquivalentsAtCarryingValue" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapAssetsCurrent" xlink:to="loc_us-gaapCashAndCashEquivalentsAtCarryingValue" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestrictedCashCurrent" xlink:label="loc_us-gaapRestrictedCashCurrent" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapAssetsCurrent" xlink:to="loc_us-gaapRestrictedCashCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountsReceivableNetCurrent" xlink:label="loc_us-gaapAccountsReceivableNetCurrent" />
      <link:calculationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapAssetsCurrent" xlink:to="loc_us-gaapAccountsReceivableNetCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssetsCurrent" xlink:label="loc_us-gaapOtherAssetsCurrent" />
      <link:calculationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapAssetsCurrent" xlink:to="loc_us-gaapOtherAssetsCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ContractWithCustomerAssetNetCurrent" xlink:label="loc_us-gaapContractWithCustomerAssetNetCurrent" />
      <link:calculationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapAssetsCurrent" xlink:to="loc_us-gaapContractWithCustomerAssetNetCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Assets" xlink:label="loc_us-gaapAssets" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapAssets" xlink:to="loc_us-gaapAssetsCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaapPropertyPlantAndEquipmentNet" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapAssets" xlink:to="loc_us-gaapPropertyPlantAndEquipmentNet" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestrictedCashNoncurrent" xlink:label="loc_us-gaapRestrictedCashNoncurrent" />
      <link:calculationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapAssets" xlink:to="loc_us-gaapRestrictedCashNoncurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset" xlink:label="loc_us-gaapOperatingLeaseRightOfUseAsset" />
      <link:calculationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapAssets" xlink:to="loc_us-gaapOperatingLeaseRightOfUseAsset" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesCurrent" xlink:label="loc_us-gaapLiabilitiesCurrent" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountsPayableCurrent" xlink:label="loc_us-gaapAccountsPayableCurrent" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapLiabilitiesCurrent" xlink:to="loc_us-gaapAccountsPayableCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccruedLiabilitiesCurrent" xlink:label="loc_us-gaapAccruedLiabilitiesCurrent" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapLiabilitiesCurrent" xlink:to="loc_us-gaapAccruedLiabilitiesCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DerivativeLiabilitiesCurrent" xlink:label="loc_us-gaapDerivativeLiabilitiesCurrent" />
      <link:calculationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapLiabilitiesCurrent" xlink:to="loc_us-gaapDerivativeLiabilitiesCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ContractWithCustomerLiabilityCurrent" xlink:label="loc_us-gaapContractWithCustomerLiabilityCurrent" />
      <link:calculationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapLiabilitiesCurrent" xlink:to="loc_us-gaapContractWithCustomerLiabilityCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiabilityCurrent" xlink:label="loc_us-gaapOperatingLeaseLiabilityCurrent" />
      <link:calculationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapLiabilitiesCurrent" xlink:to="loc_us-gaapOperatingLeaseLiabilityCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Liabilities" xlink:label="loc_us-gaapLiabilities" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapLiabilities" xlink:to="loc_us-gaapLiabilitiesCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredRentCreditNoncurrent" xlink:label="loc_us-gaapDeferredRentCreditNoncurrent" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapLiabilities" xlink:to="loc_us-gaapDeferredRentCreditNoncurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent" xlink:label="loc_us-gaapOperatingLeaseLiabilityNoncurrent" />
      <link:calculationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapLiabilities" xlink:to="loc_us-gaapOperatingLeaseLiabilityNoncurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CapitalLeaseObligationsCurrent" xlink:label="loc_us-gaapCapitalLeaseObligationsCurrent" />
      <link:calculationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapLiabilities" xlink:to="loc_us-gaapCapitalLeaseObligationsCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="loc_us-gaapStockholdersEquity" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PreferredStockValue" xlink:label="loc_us-gaapPreferredStockValue" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapStockholdersEquity" xlink:to="loc_us-gaapPreferredStockValue" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockValue" xlink:label="loc_us-gaapCommonStockValue" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapStockholdersEquity" xlink:to="loc_us-gaapCommonStockValue" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockValue" xlink:label="loc_us-gaapTreasuryStockValue" />
      <link:calculationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapStockholdersEquity" xlink:to="loc_us-gaapTreasuryStockValue" xlink:type="arc" weight="-1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="loc_us-gaapRetainedEarningsAccumulatedDeficit" />
      <link:calculationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapStockholdersEquity" xlink:to="loc_us-gaapRetainedEarningsAccumulatedDeficit" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaapAccumulatedOtherComprehensiveIncomeLossNetOfTax" />
      <link:calculationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapStockholdersEquity" xlink:to="loc_us-gaapAccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdditionalPaidInCapital" xlink:label="loc_us-gaapAdditionalPaidInCapital" />
      <link:calculationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapStockholdersEquity" xlink:to="loc_us-gaapAdditionalPaidInCapital" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="loc_us-gaapLiabilitiesAndStockholdersEquity" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommitmentsAndContingencies" xlink:label="loc_us-gaapCommitmentsAndContingencies" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapLiabilitiesAndStockholdersEquity" xlink:to="loc_us-gaapCommitmentsAndContingencies" xlink:type="arc" weight="1" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapLiabilitiesAndStockholdersEquity" xlink:to="loc_us-gaapLiabilities" xlink:type="arc" weight="1" />
      <link:calculationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapLiabilitiesAndStockholdersEquity" xlink:to="loc_us-gaapStockholdersEquity" xlink:type="arc" weight="1" />
    </link:calculationLink>
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/BalanceSheetsParenthetical" xlink:title="00000003 - Statement - Consolidated Balance Sheets (Parenthetical)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/StatementsOfOperations" xlink:title="00000004 - Statement - Consolidated Statements of Operations">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GrossProfit" xlink:label="loc_us-gaapGrossProfit" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CostOfRevenue" xlink:label="loc_us-gaapCostOfRevenue" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapGrossProfit" xlink:to="loc_us-gaapCostOfRevenue" xlink:type="arc" weight="-1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="loc_us-gaapRevenueFromContractWithCustomerExcludingAssessedTax" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapGrossProfit" xlink:to="loc_us-gaapRevenueFromContractWithCustomerExcludingAssessedTax" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingExpenses" xlink:label="loc_us-gaapOperatingExpenses" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost" xlink:label="loc_us-gaapResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapOperatingExpenses" xlink:to="loc_us-gaapResearchAndDevelopmentExpenseExcludingAcquiredInProcessCost" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpense" xlink:label="loc_us-gaapSellingGeneralAndAdministrativeExpense" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapOperatingExpenses" xlink:to="loc_us-gaapSellingGeneralAndAdministrativeExpense" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="loc_us-gaapOperatingIncomeLoss" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapOperatingIncomeLoss" xlink:to="loc_us-gaapGrossProfit" xlink:type="arc" weight="1" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapOperatingIncomeLoss" xlink:to="loc_us-gaapOperatingExpenses" xlink:type="arc" weight="-1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:label="loc_us-gaapIncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapIncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:to="loc_us-gaapOperatingIncomeLoss" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAdjustmentOfWarrants" xlink:label="loc_us-gaapFairValueAdjustmentOfWarrants" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapIncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:to="loc_us-gaapFairValueAdjustmentOfWarrants" xlink:type="arc" weight="-1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestIncomeExpenseNet" xlink:label="loc_us-gaapInterestIncomeExpenseNet" />
      <link:calculationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapIncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:to="loc_us-gaapInterestIncomeExpenseNet" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ForeignCurrencyTransactionGainLossBeforeTax" xlink:label="loc_us-gaapForeignCurrencyTransactionGainLossBeforeTax" />
      <link:calculationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapIncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:to="loc_us-gaapForeignCurrencyTransactionGainLossBeforeTax" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaapNetIncomeLoss" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetIncomeLoss" xlink:to="loc_us-gaapIncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="loc_us-gaapIncomeTaxExpenseBenefit" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetIncomeLoss" xlink:to="loc_us-gaapIncomeTaxExpenseBenefit" xlink:type="arc" weight="-1" />
    </link:calculationLink>
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/StatementsOfComprehensiveLoss" xlink:title="00000005 - Statement - Consolidated Statements of Comprehensive Loss">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaapComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaapNetIncomeLoss" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" xlink:to="loc_us-gaapNetIncomeLoss" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax" xlink:label="loc_us-gaapOtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest" xlink:to="loc_us-gaapOtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax" xlink:type="arc" weight="1" />
    </link:calculationLink>
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/StatementsOfStockholdersEquity" xlink:title="00000006 - Statement - Consolidated Statements of Stockholders&apos; Equity" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/StatementsOfCashFlows" xlink:title="00000007 - Statement - Consolidated Statements of Cash Flows">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="loc_us-gaapNetCashProvidedByUsedInOperatingActivities" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaapNetIncomeLoss" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInOperatingActivities" xlink:to="loc_us-gaapNetIncomeLoss" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ForeignCurrencyTransactionGainLossBeforeTax" xlink:label="loc_us-gaapForeignCurrencyTransactionGainLossBeforeTax" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInOperatingActivities" xlink:to="loc_us-gaapForeignCurrencyTransactionGainLossBeforeTax" xlink:type="arc" weight="-1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization" xlink:label="loc_us-gaapDepreciationDepletionAndAmortization" />
      <link:calculationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInOperatingActivities" xlink:to="loc_us-gaapDepreciationDepletionAndAmortization" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensation" xlink:label="loc_us-gaapShareBasedCompensation" />
      <link:calculationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInOperatingActivities" xlink:to="loc_us-gaapShareBasedCompensation" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAdjustmentOfWarrants" xlink:label="loc_us-gaapFairValueAdjustmentOfWarrants" />
      <link:calculationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInOperatingActivities" xlink:to="loc_us-gaapFairValueAdjustmentOfWarrants" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:label="loc_us-gaapIncreaseDecreaseInAccountsReceivable" />
      <link:calculationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInOperatingActivities" xlink:to="loc_us-gaapIncreaseDecreaseInAccountsReceivable" xlink:type="arc" weight="-1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerAsset" xlink:label="loc_us-gaapIncreaseDecreaseInContractWithCustomerAsset" />
      <link:calculationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInOperatingActivities" xlink:to="loc_us-gaapIncreaseDecreaseInContractWithCustomerAsset" xlink:type="arc" weight="-1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets" xlink:label="loc_us-gaapIncreaseDecreaseInOtherOperatingAssets" />
      <link:calculationArc order="8" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInOperatingActivities" xlink:to="loc_us-gaapIncreaseDecreaseInOtherOperatingAssets" xlink:type="arc" weight="-1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsPayable" xlink:label="loc_us-gaapIncreaseDecreaseInAccountsPayable" />
      <link:calculationArc order="9" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInOperatingActivities" xlink:to="loc_us-gaapIncreaseDecreaseInAccountsPayable" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInAccruedLiabilities" xlink:label="loc_us-gaapIncreaseDecreaseInAccruedLiabilities" />
      <link:calculationArc order="10" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInOperatingActivities" xlink:to="loc_us-gaapIncreaseDecreaseInAccruedLiabilities" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInDeferredLiabilities" xlink:label="loc_us-gaapIncreaseDecreaseInDeferredLiabilities" />
      <link:calculationArc order="11" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInOperatingActivities" xlink:to="loc_us-gaapIncreaseDecreaseInDeferredLiabilities" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInDeferredCompensation" xlink:label="loc_us-gaapIncreaseDecreaseInDeferredCompensation" />
      <link:calculationArc order="12" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInOperatingActivities" xlink:to="loc_us-gaapIncreaseDecreaseInDeferredCompensation" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerLiability" xlink:label="loc_us-gaapIncreaseDecreaseInContractWithCustomerLiability" />
      <link:calculationArc order="13" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInOperatingActivities" xlink:to="loc_us-gaapIncreaseDecreaseInContractWithCustomerLiability" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInDeferredRevenue" xlink:label="loc_us-gaapIncreaseDecreaseInDeferredRevenue" />
      <link:calculationArc order="14" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInOperatingActivities" xlink:to="loc_us-gaapIncreaseDecreaseInDeferredRevenue" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="optt-20200430.xsd#OPTT_IncreaseDecreaseInUnbilledReceivable" xlink:label="loc_OPTTIncreaseDecreaseInUnbilledReceivable" />
      <link:calculationArc order="15" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInOperatingActivities" xlink:to="loc_OPTTIncreaseDecreaseInUnbilledReceivable" xlink:type="arc" weight="-1" />
      <link:loc xlink:type="locator" xlink:href="optt-20200430.xsd#OPTT_IncreaseDecreaseInLeaseLiability" xlink:label="loc_OPTTIncreaseDecreaseInLeaseLiability" />
      <link:calculationArc order="16" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInOperatingActivities" xlink:to="loc_OPTTIncreaseDecreaseInLeaseLiability" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense" xlink:label="loc_us-gaapOperatingLeaseRightOfUseAssetAmortizationExpense" />
      <link:calculationArc order="17" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInOperatingActivities" xlink:to="loc_us-gaapOperatingLeaseRightOfUseAssetAmortizationExpense" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:label="loc_us-gaapNetCashProvidedByUsedInInvestingActivities" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquireMarketableSecurities" xlink:label="loc_us-gaapPaymentsToAcquireMarketableSecurities" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInInvestingActivities" xlink:to="loc_us-gaapPaymentsToAcquireMarketableSecurities" xlink:type="arc" weight="-1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities" xlink:label="loc_us-gaapProceedsFromSaleAndMaturityOfMarketableSecurities" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInInvestingActivities" xlink:to="loc_us-gaapProceedsFromSaleAndMaturityOfMarketableSecurities" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquireProductiveAssets" xlink:label="loc_us-gaapPaymentsToAcquireProductiveAssets" />
      <link:calculationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInInvestingActivities" xlink:to="loc_us-gaapPaymentsToAcquireProductiveAssets" xlink:type="arc" weight="-1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="loc_us-gaapNetCashProvidedByUsedInFinancingActivities" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RepaymentsOfLongTermCapitalLeaseObligations" xlink:label="loc_us-gaapRepaymentsOfLongTermCapitalLeaseObligations" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInFinancingActivities" xlink:to="loc_us-gaapRepaymentsOfLongTermCapitalLeaseObligations" xlink:type="arc" weight="-1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock" xlink:label="loc_us-gaapPaymentsForRepurchaseOfCommonStock" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInFinancingActivities" xlink:to="loc_us-gaapPaymentsForRepurchaseOfCommonStock" xlink:type="arc" weight="-1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromIssuanceInitialPublicOffering" xlink:label="loc_us-gaapProceedsFromIssuanceInitialPublicOffering" />
      <link:calculationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInFinancingActivities" xlink:to="loc_us-gaapProceedsFromIssuanceInitialPublicOffering" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:label="loc_us-gaapProceedsFromIssuanceOfCommonStock" />
      <link:calculationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInFinancingActivities" xlink:to="loc_us-gaapProceedsFromIssuanceOfCommonStock" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="optt-20200430.xsd#OPTT_ProceedsFromIssuanceOfCommonStockCommonAndPrefundedWarrantsNetOfIssuanceCosts" xlink:label="loc_OPTTProceedsFromIssuanceOfCommonStockCommonAndPrefundedWarrantsNetOfIssuanceCosts" />
      <link:calculationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInFinancingActivities" xlink:to="loc_OPTTProceedsFromIssuanceOfCommonStockCommonAndPrefundedWarrantsNetOfIssuanceCosts" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="optt-20200430.xsd#OPTT_ProceedsFromRepaymentsOfPrefundedWarrants" xlink:label="loc_OPTTProceedsFromRepaymentsOfPrefundedWarrants" />
      <link:calculationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapNetCashProvidedByUsedInFinancingActivities" xlink:to="loc_OPTTProceedsFromRepaymentsOfPrefundedWarrants" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:label="loc_us-gaapCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:to="loc_us-gaapNetCashProvidedByUsedInOperatingActivities" xlink:type="arc" weight="1" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:to="loc_us-gaapNetCashProvidedByUsedInInvestingActivities" xlink:type="arc" weight="1" />
      <link:calculationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:to="loc_us-gaapNetCashProvidedByUsedInFinancingActivities" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:label="loc_us-gaapEffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" />
      <link:calculationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:to="loc_us-gaapEffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:type="arc" weight="1" />
    </link:calculationLink>
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/BackgroundAndLiquidity" xlink:title="00000008 - Disclosure - Background and Liquidity" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/SummaryOfSignificantAccountingPolicies" xlink:title="00000009 - Disclosure - Summary of Significant Accounting Policies" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/AccountReceivableContractAssetsAndContractLiabilities" xlink:title="00000010 - Disclosure - Account Receivable, Contract Assets, and Contract Liabilities" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/OtherCurrentAssets" xlink:title="00000011 - Disclosure - Other Current Assets" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/PropertyAndEquipment" xlink:title="00000012 - Disclosure - Property and Equipment" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/Leases" xlink:title="00000013 - Disclosure - Leases" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/AccruedExpenses" xlink:title="00000014 - Disclosure - Accrued Expenses" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/Warrants" xlink:title="00000015 - Disclosure - Warrants" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/PreferredStock" xlink:title="00000016 - Disclosure - Preferred Stock" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/CommonStock" xlink:title="00000017 - Disclosure - Common Stock" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/TreasuryShares" xlink:title="00000018 - Disclosure - Treasury Shares" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/Share-basedCompensationPlans" xlink:title="00000019 - Disclosure - Share-Based Compensation Plans" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/FairValueMeasurements" xlink:title="00000020 - Disclosure - Fair Value Measurements" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/IncomeTaxes" xlink:title="00000021 - Disclosure - Income Taxes" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/CommitmentsAndContingencies" xlink:title="00000022 - Disclosure - Commitments and Contingencies" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/OperatingSegmentsAndGeographicInformation" xlink:title="00000023 - Disclosure - Operating Segments and Geographic Information" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/SubsequentEvent" xlink:title="00000024 - Disclosure - Subsequent Event" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/SummaryOfSignificantAccountingPoliciesPolicies" xlink:title="00000025 - Disclosure - Summary of Significant Accounting Policies (Policies)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/SummaryOfSignificantAccountingPoliciesTables" xlink:title="00000026 - Disclosure - Summary of Significant Accounting Policies (Tables)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/AccountReceivableContractAssetsAndContractLiabilitiesTables" xlink:title="00000027 - Disclosure - Account Receivable, Contract Assets, and Contract Liabilities (Tables)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/OtherCurrentAssetsTables" xlink:title="00000028 - Disclosure - Other Current Assets (Tables)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/PropertyAndEquipmentTables" xlink:title="00000029 - Disclosure - Property and Equipment (Tables)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/LeasesTables" xlink:title="00000030 - Disclosure - Leases (Tables)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/AccruedExpensesTables" xlink:title="00000031 - Disclosure - Accrued Expenses (Tables)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/WarrantsTables" xlink:title="00000032 - Disclosure - Warrants (Tables)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/Stock-basedCompensationTables" xlink:title="00000033 - Disclosure - Stock-Based Compensation (Tables)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/FairValueMeasurementsTables" xlink:title="00000034 - Disclosure - Fair Value Measurements (Tables)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/IncomeTaxesTables" xlink:title="00000035 - Disclosure - Income Taxes (Tables)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/OperatingSegmentsAndGeographicInformationTables" xlink:title="00000036 - Disclosure - Operating Segments and Geographic Information (Tables)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/BackgroundAndLiquidityDetailsNarrative" xlink:title="00000037 - Disclosure - Background and Liquidity (Details Narrative)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/SummaryOfSignificantAccountingPoliciesDetailsNarrative" xlink:title="00000038 - Disclosure - Summary of Significant Accounting Policies (Details Narrative)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/SummaryOfSignificantAccountingPolicies-ScheduleOfCashAndCashEquivalentsDetails" xlink:title="00000039 - Disclosure - Summary of Significant Accounting Policies - Schedule of Cash and Cash Equivalents (Details)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/SummaryOfSignificantAccountingPolicies-ScheduleOfCashAndCashEquivalentsAndRestrictedCashDetails" xlink:title="00000040 - Disclosure - Summary of Significant Accounting Policies - Schedule of Cash and Cash Equivalents and Restricted Cash (Details)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/SummaryOfSignificantAccountingPolicies-ScheduleOfPropertyPlantAndEquipmentUsefulLifeDetails" xlink:title="00000041 - Disclosure - Summary of Significant Accounting Policies - Schedule of Property, Plant and Equipment, Useful Life (Details)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/SummaryOfSignificantAccountingPolicies-ScheduleOfRevenueByMajorCustomersByReportingSegmentsDetails" xlink:title="00000042 - Disclosure - Summary of Significant Accounting Policies - Schedule of Revenue by Major Customers by Reporting Segments (Details)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/SummaryOfSignificantAccountingPolicies-ScheduleOfEmployeeServiceShare-basedCompensationAllocationOfRecognizedPeriodCostsDetails" xlink:title="00000043 - Disclosure - Summary of Significant Accounting Policies - Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs (Details)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/AccountReceivableContractAssetsAndContractLiabilities-ScheduleOfAccountsReceivableDetails" xlink:title="00000044 - Disclosure - Account Receivable, Contract Assets, and Contract Liabilities - Schedule of Accounts Receivable (Details)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/OtherCurrentAssets-ScheduleOfOtherCurrentAssetsDetails" xlink:title="00000045 - Disclosure - Other Current Assets - Schedule of Other Current Assets (Details)">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssetsCurrent" xlink:label="loc_us-gaapOtherAssetsCurrent" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DepositsAssetsCurrent" xlink:label="loc_us-gaapDepositsAssetsCurrent" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapOtherAssetsCurrent" xlink:to="loc_us-gaapDepositsAssetsCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherReceivablesNetCurrent" xlink:label="loc_us-gaapOtherReceivablesNetCurrent" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapOtherAssetsCurrent" xlink:to="loc_us-gaapOtherReceivablesNetCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PrepaidInsurance" xlink:label="loc_us-gaapPrepaidInsurance" />
      <link:calculationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapOtherAssetsCurrent" xlink:to="loc_us-gaapPrepaidInsurance" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="optt-20200430.xsd#OPTT_PrepaidOfferingCosts" xlink:label="loc_OPTTPrepaidOfferingCosts" />
      <link:calculationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapOtherAssetsCurrent" xlink:to="loc_OPTTPrepaidOfferingCosts" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherPrepaidExpenseCurrent" xlink:label="loc_us-gaapOtherPrepaidExpenseCurrent" />
      <link:calculationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapOtherAssetsCurrent" xlink:to="loc_us-gaapOtherPrepaidExpenseCurrent" xlink:type="arc" weight="1" />
    </link:calculationLink>
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/PropertyAndEquipmentDetailsNarrative" xlink:title="00000046 - Disclosure - Property and Equipment (Details Narrative)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/PropertyAndEquipment-ScheduleOfComponentsOfPropertyAndEquipmentNetDetails" xlink:title="00000047 - Disclosure - Property and Equipment - Schedule of Components of Property and Equipment, Net (Details)">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaapPropertyPlantAndEquipmentNet" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross" xlink:label="loc_us-gaapPropertyPlantAndEquipmentGross" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapPropertyPlantAndEquipmentNet" xlink:to="loc_us-gaapPropertyPlantAndEquipmentGross" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:label="loc_us-gaapAccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapPropertyPlantAndEquipmentNet" xlink:to="loc_us-gaapAccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:type="arc" weight="-1" />
    </link:calculationLink>
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/LeasesDetailsNarrative" xlink:title="00000048 - Disclosure - Leases (Details Narrative)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/Leases-ScheduleOfRight-ofUseAssetsAndLeaseLiabilitiesDetails" xlink:title="00000049 - Disclosure - Leases - Schedule of Right-of Use Assets and Lease Liabilities (Details)">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiability" xlink:label="loc_us-gaapOperatingLeaseLiability" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiabilityCurrent" xlink:label="loc_us-gaapOperatingLeaseLiabilityCurrent" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapOperatingLeaseLiability" xlink:to="loc_us-gaapOperatingLeaseLiabilityCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent" xlink:label="loc_us-gaapOperatingLeaseLiabilityNoncurrent" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapOperatingLeaseLiability" xlink:to="loc_us-gaapOperatingLeaseLiabilityNoncurrent" xlink:type="arc" weight="1" />
    </link:calculationLink>
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/Leases-ScheduleOfRemainingLeasePaymentsUnderOperatingLeaseDetails" xlink:title="00000050 - Disclosure - Leases - Schedule of Remaining Lease Payments Under Operating Lease (Details)">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:label="loc_us-gaapLesseeOperatingLeaseLiabilityPaymentsDue" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo" xlink:label="loc_us-gaapLesseeOperatingLeaseLiabilityPaymentsDueYearTwo" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapLesseeOperatingLeaseLiabilityPaymentsDue" xlink:to="loc_us-gaapLesseeOperatingLeaseLiabilityPaymentsDueYearTwo" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree" xlink:label="loc_us-gaapLesseeOperatingLeaseLiabilityPaymentsDueYearThree" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapLesseeOperatingLeaseLiabilityPaymentsDue" xlink:to="loc_us-gaapLesseeOperatingLeaseLiabilityPaymentsDueYearThree" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour" xlink:label="loc_us-gaapLesseeOperatingLeaseLiabilityPaymentsDueYearFour" />
      <link:calculationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapLesseeOperatingLeaseLiabilityPaymentsDue" xlink:to="loc_us-gaapLesseeOperatingLeaseLiabilityPaymentsDueYearFour" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive" xlink:label="loc_us-gaapLesseeOperatingLeaseLiabilityPaymentsDueYearFive" />
      <link:calculationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapLesseeOperatingLeaseLiabilityPaymentsDue" xlink:to="loc_us-gaapLesseeOperatingLeaseLiabilityPaymentsDueYearFive" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive" xlink:label="loc_us-gaapLesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive" />
      <link:calculationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapLesseeOperatingLeaseLiabilityPaymentsDue" xlink:to="loc_us-gaapLesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive" xlink:type="arc" weight="1" />
    </link:calculationLink>
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/Leases-ScheduleOfFutureMinimumLeasePaymentsUnderOperatingLeaseDetails" xlink:title="00000051 - Disclosure - Leases - Schedule of Future Minimum Lease Payments Under Operating Lease (Details)">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDue" xlink:label="loc_us-gaapOperatingLeasesFutureMinimumPaymentsDue" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears" xlink:label="loc_us-gaapOperatingLeasesFutureMinimumPaymentsDueInTwoYears" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapOperatingLeasesFutureMinimumPaymentsDue" xlink:to="loc_us-gaapOperatingLeasesFutureMinimumPaymentsDueInTwoYears" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears" xlink:label="loc_us-gaapOperatingLeasesFutureMinimumPaymentsDueInThreeYears" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapOperatingLeasesFutureMinimumPaymentsDue" xlink:to="loc_us-gaapOperatingLeasesFutureMinimumPaymentsDueInThreeYears" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears" xlink:label="loc_us-gaapOperatingLeasesFutureMinimumPaymentsDueInFourYears" />
      <link:calculationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapOperatingLeasesFutureMinimumPaymentsDue" xlink:to="loc_us-gaapOperatingLeasesFutureMinimumPaymentsDueInFourYears" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears" xlink:label="loc_us-gaapOperatingLeasesFutureMinimumPaymentsDueInFiveYears" />
      <link:calculationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapOperatingLeasesFutureMinimumPaymentsDue" xlink:to="loc_us-gaapOperatingLeasesFutureMinimumPaymentsDueInFiveYears" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter" xlink:label="loc_us-gaapOperatingLeasesFutureMinimumPaymentsDueThereafter" />
      <link:calculationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapOperatingLeasesFutureMinimumPaymentsDue" xlink:to="loc_us-gaapOperatingLeasesFutureMinimumPaymentsDueThereafter" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear" xlink:label="loc_us-gaapOperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear" />
      <link:calculationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapOperatingLeasesFutureMinimumPaymentsDue" xlink:to="loc_us-gaapOperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear" xlink:type="arc" weight="1" />
    </link:calculationLink>
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/AccruedExpenses-ScheduleOfAccruedExpensesDetails" xlink:title="00000052 - Disclosure - Accrued Expenses - Schedule of Accrued Expenses (Details)">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccruedLiabilitiesCurrent" xlink:label="loc_us-gaapAccruedLiabilitiesCurrent" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAccruedLiabilitiesCurrent" xlink:label="loc_us-gaapOtherAccruedLiabilitiesCurrent" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapAccruedLiabilitiesCurrent" xlink:to="loc_us-gaapOtherAccruedLiabilitiesCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LossContingencyAccrualCarryingValueCurrent" xlink:label="loc_us-gaapLossContingencyAccrualCarryingValueCurrent" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapAccruedLiabilitiesCurrent" xlink:to="loc_us-gaapLossContingencyAccrualCarryingValueCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ConstructionPayableCurrent" xlink:label="loc_us-gaapConstructionPayableCurrent" />
      <link:calculationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapAccruedLiabilitiesCurrent" xlink:to="loc_us-gaapConstructionPayableCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccruedSalariesCurrent" xlink:label="loc_us-gaapAccruedSalariesCurrent" />
      <link:calculationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapAccruedLiabilitiesCurrent" xlink:to="loc_us-gaapAccruedSalariesCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherEmployeeRelatedLiabilitiesCurrent" xlink:label="loc_us-gaapOtherEmployeeRelatedLiabilitiesCurrent" />
      <link:calculationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapAccruedLiabilitiesCurrent" xlink:to="loc_us-gaapOtherEmployeeRelatedLiabilitiesCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccruedIncomeTaxesCurrent" xlink:label="loc_us-gaapAccruedIncomeTaxesCurrent" />
      <link:calculationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapAccruedLiabilitiesCurrent" xlink:to="loc_us-gaapAccruedIncomeTaxesCurrent" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccruedProfessionalFeesCurrent" xlink:label="loc_us-gaapAccruedProfessionalFeesCurrent" />
      <link:calculationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapAccruedLiabilitiesCurrent" xlink:to="loc_us-gaapAccruedProfessionalFeesCurrent" xlink:type="arc" weight="1" />
    </link:calculationLink>
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/WarrantsDetailsNarrative" xlink:title="00000053 - Disclosure - Warrants (Details Narrative)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/Warrants-ScheduleOfFairValueAssumptionsUsedDetails" xlink:title="00000054 - Disclosure - Warrants - Schedule of Fair Value Assumptions Used (Details)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/PreferredStockDetailsNarrative" xlink:title="00000055 - Disclosure - Preferred Stock (Details Narrative)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/CommonStockDetailsNarrative" xlink:title="00000056 - Disclosure - Common Stock (Details Narrative)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/TreasurySharesDetailsNarrative" xlink:title="00000057 - Disclosure - Treasury Shares (Details Narrative)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/Share-basedCompensationDetailsNarrative" xlink:title="00000058 - Disclosure - Share-Based Compensation (Details Narrative)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/Share-basedCompensationPlans-ScheduleOfShare-basedPaymentAwardStockOptionsValuationAssumptionsDetails" xlink:title="00000059 - Disclosure - Share-Based Compensation Plans - Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions (Details)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/Share-basedCompensationPlans-ScheduleOfStockOptionActivityDetails" xlink:title="00000060 - Disclosure - Share-Based Compensation Plans - Schedule of Stock Option Activity (Details)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/Share-basedCompensationPlans-ScheduleOfNon-vestedRestrictedStockActivityDetails" xlink:title="00000061 - Disclosure - Share-Based Compensation Plans - Schedule of Non-vested Restricted Stock Activity (Details)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/FairValueMeasurements-ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisDetails" xlink:title="00000062 - Disclosure - Fair Value Measurements - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/FairValueMeasurements-SummaryOfChangesOnValueOfWarrantLiabilityUsingSignificantUnobservableInputsDetails" xlink:title="00000063 - Disclosure - Fair Value Measurements - Summary of Changes on Value of Warrant Liability Using Significant Unobservable Inputs (Details)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/IncomeTaxesDetailsNarrative" xlink:title="00000064 - Disclosure - Income Taxes (Details Narrative)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/IncomeTaxes-ScheduleOfComponentsOfLossBeforeIncomeTaxesDetails" xlink:title="00000065 - Disclosure - Income Taxes - Schedule of Components of Loss Before Income Taxes (Details)">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:label="loc_us-gaapIncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic" xlink:label="loc_us-gaapIncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapIncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:to="loc_us-gaapIncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign" xlink:label="loc_us-gaapIncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapIncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:to="loc_us-gaapIncomeLossFromContinuingOperationsBeforeIncomeTaxesForeign" xlink:type="arc" weight="1" />
    </link:calculationLink>
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/IncomeTaxes-ScheduleOfEffectiveIncomeTaxRateReconciliationDetails" xlink:title="00000066 - Disclosure - Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/IncomeTaxes-ScheduleOfDeferredTaxAssetsAndLiabilitiesDetails" xlink:title="00000067 - Disclosure - Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details)">
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsGross" xlink:label="loc_us-gaapDeferredTaxAssetsGross" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic" xlink:label="loc_us-gaapDeferredTaxAssetsOperatingLossCarryforwardsDomestic" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapDeferredTaxAssetsGross" xlink:to="loc_us-gaapDeferredTaxAssetsOperatingLossCarryforwardsDomestic" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsForeign" xlink:label="loc_us-gaapDeferredTaxAssetsOperatingLossCarryforwardsForeign" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapDeferredTaxAssetsGross" xlink:to="loc_us-gaapDeferredTaxAssetsOperatingLossCarryforwardsForeign" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsStateAndLocal" xlink:label="loc_us-gaapDeferredTaxAssetsOperatingLossCarryforwardsStateAndLocal" />
      <link:calculationArc order="3" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapDeferredTaxAssetsGross" xlink:to="loc_us-gaapDeferredTaxAssetsOperatingLossCarryforwardsStateAndLocal" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsTaxCreditCarryforwardsResearch" xlink:label="loc_us-gaapDeferredTaxAssetsTaxCreditCarryforwardsResearch" />
      <link:calculationArc order="4" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapDeferredTaxAssetsGross" xlink:to="loc_us-gaapDeferredTaxAssetsTaxCreditCarryforwardsResearch" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost" xlink:label="loc_us-gaapDeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost" />
      <link:calculationArc order="5" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapDeferredTaxAssetsGross" xlink:to="loc_us-gaapDeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities" xlink:label="loc_us-gaapDeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities" />
      <link:calculationArc order="6" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapDeferredTaxAssetsGross" xlink:to="loc_us-gaapDeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAccruedLiabilities" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsOther" xlink:label="loc_us-gaapDeferredTaxAssetsOther" />
      <link:calculationArc order="7" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapDeferredTaxAssetsGross" xlink:to="loc_us-gaapDeferredTaxAssetsOther" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsLiabilitiesNet" xlink:label="loc_us-gaapDeferredTaxAssetsLiabilitiesNet" />
      <link:calculationArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapDeferredTaxAssetsLiabilitiesNet" xlink:to="loc_us-gaapDeferredTaxAssetsGross" xlink:type="arc" weight="1" />
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredTaxAssetsValuationAllowance" xlink:label="loc_us-gaapDeferredTaxAssetsValuationAllowance" />
      <link:calculationArc order="2" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="loc_us-gaapDeferredTaxAssetsLiabilitiesNet" xlink:to="loc_us-gaapDeferredTaxAssetsValuationAllowance" xlink:type="arc" weight="-1" />
    </link:calculationLink>
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/CommitmentsAndContingenciesDetailsNarrative" xlink:title="00000068 - Disclosure - Commitments and Contingencies (Details Narrative)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/OperatingSegmentsAndGeographicInformationDetailsNarrative" xlink:title="00000069 - Disclosure - Operating Segments and Geographic Information (Details Narrative)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/OperatingSegmentsAndGeographicInformation-ScheduleOfRevenueFromExternalCustomersAndLong-livedAssetsByGeographicalAreasDetails" xlink:title="00000070 - Disclosure - Operating Segments and Geographic Information - Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas (Details)" />
    <link:calculationLink xlink:type="extended" xlink:role="http://oceanpowertechnologies.com/role/SubsequentEventDetailsNarrative" xlink:title="00000071 - Disclosure - Subsequent Event (Details Narrative)" />
</link:linkbase>
