<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2024-01-02</periodOfReport>

    <issuer>
        <issuerCik>0000009092</issuerCik>
        <issuerName>BADGER METER INC</issuerName>
        <issuerTradingSymbol>BMI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001525211</rptOwnerCik>
            <rptOwnerName>ADAMS TODD A.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>4545 W. BROWN DEER ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>MILWAUKEE</rptOwnerCity>
            <rptOwnerState>WI</rptOwnerState>
            <rptOwnerZipCode>53223</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>true</isDirector>
            <isOfficer>false</isOfficer>
            <isTenPercentOwner>false</isTenPercentOwner>
            <isOther>false</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>false</aff10b5One>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2024-01-02</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>false</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>103.65</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>154.37</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>BMI Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>103.65</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>14075.913</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Each share of phantom stock is the economic equivalent of one share of common stock. The shares of phantom stock become payable in cash upon the reporting person's termination of service as a director.</footnote>
        <footnote id="F2">The phantom stock units were accrued in Mr. Adams' Badger Meter, Inc. Director Deferred Compensation Plan account as payment for his 2024 First Quarter retainer of $16,000. The phantom stock units were computed at $154.37, the 12/29/2023 closing price of the Company's common stock as required by the plan.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ William R.A. Bergum, Attorney-in-Fact for Todd A. Adams</signatureName>
        <signatureDate>2024-01-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
