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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2015-08-06</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001637207</issuerCik>
        <issuerName>Planet Fitness, Inc.</issuerName>
        <issuerTradingSymbol>PLNT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001649775</rptOwnerCik>
            <rptOwnerName>Wong Edward B</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O TSG CONSUMER PARTNERS, LLC</rptOwnerStreet1>
            <rptOwnerStreet2>600 MONTGOMERY STREET, SUITE 2900</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94111</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <footnotes></footnotes>

    <remarks>R. Wallace Wertsch is signing on behalf of Edward B. Wong pursuant to a Power of Attorney dated July 29, 2015, which is attached hereto as an exhibit.</remarks>

    <ownerSignature>
        <signatureName>/s/ R. Wallace Wertsch, attorney-in-fact</signatureName>
        <signatureDate>2015-08-06</signatureDate>
    </ownerSignature>
</ownershipDocument>
