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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2012-11-12</periodOfReport>

    <issuer>
        <issuerCik>0000835729</issuerCik>
        <issuerName>BMC SOFTWARE INC</issuerName>
        <issuerTradingSymbol>BMC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001007549</rptOwnerCik>
            <rptOwnerName>SOLCHER STEPHEN B</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2101 CITYWEST BLVD.</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>HOUSTON</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>77042</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isOfficer>1</isOfficer>
            <officerTitle>Sr VP, CFO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2012-11-12</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>19814</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>109403</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Performance-based Market Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F2"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2012-11-12</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>18080</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>18080</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>18080</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Award of time-based restricted stock units under BMC Software, Inc. 2007 Employee Incentive Plan.  The time-based restricted stock units shall vest based on continuous employment, 1/3 per year over three years.</footnote>
        <footnote id="F2">Each performance-based market stock unit (MSU) represents the right to receive, following vesting, up to 150% of one share of BMC common stock.  The actual number of shares of BMC common stock acquired upon vesting of the performance-based MSUs can range from 0% to 150% of the number of MSUs awarded and is contingent upon the achievement of pre-established performance metrics, as approved by BMC's Compensation Committee.  One half of the performance-based MSUs are subject to vesting two years after the award date, and one half are subject to vesting three years after the award date; provided, that any unvested MSUs after two years rollover and are eligible to vest after three years.</footnote>
        <footnote id="F3">Unless earlier forfeited under the terms of the performance-based MSU award agreement, each performance-based MSU converts into up to 150% of one share of BMC common stock based upon performance vesting.  One half of the performance-based MSUs will vest based upon performance over a two year period ending two years after the award date, and one half of the performance-based MSUs will vest based upon performance over a three year period ending three years after the award date; provided, that any unvested MSUs after two years rollover and are eligible to vest after three years.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Christopher C. Chaffin, Attorney-in-fact for Stephen Boyd Solcher</signatureName>
        <signatureDate>2012-11-13</signatureDate>
    </ownerSignature>
</ownershipDocument>
