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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2008-01-16</periodOfReport>

    <dateOfOriginalSubmission>2008-01-16</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000077597</issuerCik>
        <issuerName>SPARTECH CORP</issuerName>
        <issuerTradingSymbol>SEH</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001229521</rptOwnerCik>
            <rptOwnerName>ANDY RALPH B</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O SPARTECH CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>120 S. CENTRAL AVENUE, SUITE 1700</rptOwnerStreet2>
            <rptOwnerCity>CLAYTON</rptOwnerCity>
            <rptOwnerState>MO</rptOwnerState>
            <rptOwnerZipCode>63105</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>75484</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2008-01-16</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>200000</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>14.06</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>350261</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Corporation / Limited Partnership</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The limited partnership purchased 200,000 shares of common stock directly from the issuer pursuant to a Stock Purchase Agreement dated January 15, 2008.  This transaction was reported on a timely filed Form 4 on January 16, 2008.</footnote>
        <footnote id="F2">Reporting person owns 100% of the common stock in a corporation which owns a .1% general partnership interest in a limited partnership.  The limited partnership owns 350,261 shares of Spartech Corporation common stock.

The reporting person has sole investment and voting power over these shares as President and sole shareholder of the corporation which is general partner of the limited partnership.  As such the reporting person is filing an amended Form 4 to report 100% of the holdings of the limited partnership pursuant to Instruction 4(b)(iv) of Form 4.  Previously, the reporting person chose only to report his proportionate interest through his .1% indirect ownership as sole owner of the corporate general partner.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Randy C. Ridenhour, Power of Attorney for Ralph B. Andy</signatureName>
        <signatureDate>2008-01-24</signatureDate>
    </ownerSignature>
</ownershipDocument>
