Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	497
Document Period End Date	dei_DocumentPeriodEndDate	Feb. 28, 2017
Registrant Name	dei_EntityRegistrantName	PUTNAM MULTI-CAP GROWTH FUND
Central Index Key	dei_EntityCentralIndexKey	0000865177
Amendment Flag	dei_AmendmentFlag	false
Trading Symbol	dei_TradingSymbol	PNOPX
Document Creation Date	dei_DocumentCreationDate	Mar. 13, 2017
Document Effective Date	dei_DocumentEffectiveDate	Apr. 01, 2017
Prospectus Date	rr_ProspectusDate	Oct. 30, 2016
Putnam Multi-Cap Growth Fund
Risk/Return:	rr_RiskReturnAbstract
Expense [Heading]	rr_ExpenseHeading	Fees and expenses
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	The following table describes the fees and expenses you may pay if you buy and hold shares of the fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Putnam funds. More information about these and other discounts is available from your financial advisor and in How do I buy fund shares? beginning on page 11 of the fund’s prospectus, in the Appendix to the fund’s prospectus, and in How to buy shares beginning on page II-1 of the fund’s statement of additional information (SAI).
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder fees (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual fund operating expenses (expenses you pay each year as a percentage of the value of your investment)
Expense Breakpoint Discounts [Text]	rr_ExpenseBreakpointDiscounts	You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Putnam funds. More information about these and other discounts is available from your financial advisor and in How do I buy fund shares? beginning on page 11 of the fund’s prospectus, in the Appendix to the fund’s prospectus, and in How to buy shares beginning on page II-1 of the fund’s statement of additional information (SAI).
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	$ 50,000
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	The following hypothetical example is intended to help you compare the cost of investing in the fund with the cost of investing in other funds. It assumes that you invest $10,000 in the fund for the time periods indicated and then, except as indicated, redeem all your shares at the end of those periods. It assumes a 5% return on your investment each year and that the fund’s operating expenses remain the same. Your actual costs may be higher or lower.
Putnam Multi-Cap Growth Fund | Class T
Risk/Return:	rr_RiskReturnAbstract
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	2.50%
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, whichever is lower)	rr_MaximumDeferredSalesChargeOverOther	none
Management fees	rr_ManagementFeesOverAssets	0.53%	[1]
Distribution and service (12b-1) fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other expenses	rr_OtherExpensesOverAssets	0.27%	[2]
Total annual fund operating expenses	rr_ExpensesOverAssets	1.05%
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	$ 354
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	576
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	815
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	$ 1,500

[1] Management fees reflect a performance adjustment. The fund's base management fee is subject to adjustment, up or down, based on the fund's performance relative to the performance of the Russell 3000 Growth Index. For the most recent fiscal year, the fund's base management fee prior to any performance adjustment was 0.553%.

[2] Other expenses are based on expenses of class A shares for the fund's last fiscal year.