Label

Element

Value

Risk/Return:

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Registrant Name

dei_EntityRegistrantName

BLACKROCK FUNDS

Prospectus Date

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Aug. 12, 2015

Supplement [Text Block]

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BLACKROCK FUNDS^SM
BlackRock Total Stock Market Index Fund
(the "Fund")

     Supplement dated November 10, 2015
to the Class K Shares Prospectus of the Fund, dated August 12, 2015

Effective immediately, BlackRock (as defined below) has agreed contractually to cap net expenses of the Fund at a lower level. To achieve this expense cap, BlackRock has agreed to waive and/or reimburse fees or expenses if the Fund's annual fund operating expenses, excluding certain expenses described in the prospectus, exceed a certain limit. Accordingly, effective immediately the Fund's prospectus is amended as follows:

The section entitled "Fund Overview — Key Facts About BlackRock Total Stock Market Index Fund —Fees and Expenses of the Fund" is deleted in its entirety and replaced with the following:

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold Class K Shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)	Class K Shares
Management Fee	0.01%
Distribution and/or Service (12b-1) Fees	None
Other Expenses1	0.15%
Total Annual Fund Operating Expenses	0.16%
Fee Waivers and/or Expense Reimbursements2	(0.13)%
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements2	0.03%

¹ Other Expenses are based on estimated amounts for the current year.

² As described in the "Management of the Fund" section of the Fund's prospectus beginning on page 19, BlackRock Advisors, LLC ("BlackRock") has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) to 0.03% of average daily net assets until November 30, 2016. The Fund may have to repay some of these waivers and/or reimbursements to BlackRock in the following two years. The agreement may be terminated upon 90 days' notice by a majority of the non-interested trustees of the Trust or by a vote of a majority of the outstanding voting securities of the Fund.

Example:

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

	1 Year	3 Years
Class K Shares	$3	$38

Portfolio Turnover:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance.

BlackRock Total Stock Market Index Fund

Risk/Return:

rr_RiskReturnAbstract

Supplement [Text Block]

bf1_SupplementTextBlock

BLACKROCK FUNDS^SM
BlackRock Total Stock Market Index Fund
(the "Fund")

     Supplement dated November 10, 2015
to the Class K Shares Prospectus of the Fund, dated August 12, 2015

Effective immediately, BlackRock (as defined below) has agreed contractually to cap net expenses of the Fund at a lower level. To achieve this expense cap, BlackRock has agreed to waive and/or reimburse fees or expenses if the Fund's annual fund operating expenses, excluding certain expenses described in the prospectus, exceed a certain limit. Accordingly, effective immediately the Fund's prospectus is amended as follows:

The section entitled "Fund Overview — Key Facts About BlackRock Total Stock Market Index Fund —Fees and Expenses of the Fund" is deleted in its entirety and replaced with the following:

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold Class K Shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)	Class K Shares
Management Fee	0.01%
Distribution and/or Service (12b-1) Fees	None
Other Expenses1	0.15%
Total Annual Fund Operating Expenses	0.16%
Fee Waivers and/or Expense Reimbursements2	(0.13)%
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements2	0.03%

¹ Other Expenses are based on estimated amounts for the current year.

² As described in the "Management of the Fund" section of the Fund's prospectus beginning on page 19, BlackRock Advisors, LLC ("BlackRock") has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) to 0.03% of average daily net assets until November 30, 2016. The Fund may have to repay some of these waivers and/or reimbursements to BlackRock in the following two years. The agreement may be terminated upon 90 days' notice by a majority of the non-interested trustees of the Trust or by a vote of a majority of the outstanding voting securities of the Fund.

Example:

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

	1 Year	3 Years
Class K Shares	$3	$38

Portfolio Turnover:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance.

Expense [Heading]

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Fees and Expenses of the Fund

Expense Narrative [Text Block]

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This table describes the fees and expenses that you may pay if you buy and hold Class K Shares of the Fund.

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses
(expenses that you pay each year as a
percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

November 30, 2016

Portfolio Turnover [Heading]

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Portfolio Turnover:

Portfolio Turnover [Text Block]

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The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance.

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other Expenses are based on estimated amounts for the current year.

Expense Example [Heading]

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Example:

Expense Example Narrative [Text Block]

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This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

BlackRock Total Stock Market Index Fund | Class K Shares

Risk/Return:

rr_RiskReturnAbstract

Management Fee

rr_ManagementFeesOverAssets

0.01%

Distribution and/or Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses

rr_OtherExpensesOverAssets

0.15%

^[1]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.16%

Fee Waivers and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.13%)

^[2]

Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements

rr_NetExpensesOverAssets

0.03%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 3

3 Years

rr_ExpenseExampleYear03

$ 38

[1] Other Expenses are based on estimated amounts for the current year.

[2] As described in the "Management of the Fund" section of the Fund's prospectus beginning on page 19, BlackRock Advisors, LLC ("BlackRock") has contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) to 0.03% of average daily net assets until November 30, 2016. The Fund may have to repay some of these waivers and/or reimbursements to BlackRock in the following two years. The agreement may be terminated upon 90 days' notice by a majority of the non-interested trustees of the Trust or by a vote of a majority of the outstanding voting securities of the Fund.