Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

BLACKROCK FUNDS

Prospectus Date

rr_ProspectusDate

Jan. 28, 2015

Supplement [Text Block]

bf11_SupplementTextBlock

BLACKROCK FUNDS^SM
BlackRock U.S. Opportunities Portfolio
(the "Fund")

     Supplement dated October 1, 2015
to the Class R Shares Prospectus of the Fund, dated January 28, 2015

Effective immediately, BlackRock (as defined below) has agreed contractually to: (i) reduce its management fee for the Fund; and (ii) 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, the Fund's prospectus is amended as follows:

The section entitled "Fund Overview — Key Facts About BlackRock U.S. Opportunities Portfolio — 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 R Shares of U.S. Opportunities.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)	Class R            Shares
Management Fees		0.93	%
Distribution and/or Service (12b-1) Fees		0.50	%
Other Expenses1		0.28	%
Total Annual Fund Operating Expenses		1.71	%
Fee Waivers and/or Expense Reimbursements2		(0.15	)%
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements2		1.56	%

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

² As described in the "Management of the Funds" section of the Fund's prospectus beginning on page 49, 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 1.56% of average daily net assets until February 1, 2017. 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. This 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 R Shares	$159	$524

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. During the most recent fiscal year, the Fund's portfolio turnover rate was 66% of the average value of its portfolio.

BLACKROCK U.S. OPPORTUNITIES PORTFOLIO

Risk/Return:

rr_RiskReturnAbstract

Supplement [Text Block]

bf11_SupplementTextBlock

BLACKROCK FUNDS^SM
BlackRock U.S. Opportunities Portfolio
(the "Fund")

     Supplement dated October 1, 2015
to the Class R Shares Prospectus of the Fund, dated January 28, 2015

Effective immediately, BlackRock (as defined below) has agreed contractually to: (i) reduce its management fee for the Fund; and (ii) 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, the Fund's prospectus is amended as follows:

The section entitled "Fund Overview — Key Facts About BlackRock U.S. Opportunities Portfolio — 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 R Shares of U.S. Opportunities.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)	Class R            Shares
Management Fees		0.93	%
Distribution and/or Service (12b-1) Fees		0.50	%
Other Expenses1		0.28	%
Total Annual Fund Operating Expenses		1.71	%
Fee Waivers and/or Expense Reimbursements2		(0.15	)%
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements2		1.56	%

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

² As described in the "Management of the Funds" section of the Fund's prospectus beginning on page 49, 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 1.56% of average daily net assets until February 1, 2017. 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. This 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 R Shares	$159	$524

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. During the most recent fiscal year, the Fund's portfolio turnover rate was 66% of the average value of its portfolio.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold Class R Shares of U.S. Opportunities.

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

February 1, 2017

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover:

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

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. During the most recent fiscal year, the Fund’s portfolio turnover rate was 66% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

66.00%

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

rr_OtherExpensesNewFundBasedOnEstimates

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

Expense Example [Heading]

rr_ExpenseExampleHeading

Example:

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. This 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 U.S. OPPORTUNITIES PORTFOLIO | Class R Shares

Risk/Return:

rr_RiskReturnAbstract

Management Fees

rr_ManagementFeesOverAssets

0.93%

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

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other Expenses

rr_OtherExpensesOverAssets

0.28%

^[1]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

1.71%

Fee Waivers and/or Expense Reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.15%)

^[2]

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

rr_NetExpensesOverAssets

1.56%

^[2]

1 Year

rr_ExpenseExampleYear01

$ 159

3 Years

rr_ExpenseExampleYear03

$ 524

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

[2] As described in the "Management of the Funds" section of the Fund's prospectus beginning on page 49, 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 1.56% of average daily net assets until February 1, 2017. 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.