Excel GAMMAINV function

The Excel GAMMAINV function returns the inverse of the gamma cumulative distribution. This is a legacy function that was replaced by the GAMMA.INV function in Excel 2010. Microsoft recommends using GAMMA.INV for new work, as it provides better accuracy. For a detailed explanation of the gamma inverse distribution and practical examples, see the GAMMA.INV function.

Purpose

Get inverse of the gamma cumulative distribution

Return value

The value of a probability

Syntax

=GAMMAINV(probability,alpha,beta)

probability - The probability associated with the gamma distribution (must be between 0 and 1).
alpha - The shape parameter of the distribution.
beta - The scale parameter of the distribution.

Using the GAMMAINV function

The GAMMAINV function returns the value at which the cumulative gamma distribution reaches a specified probability. For better accuracy and consistency with other modern statistical functions, it is recommended to use the GAMMA.INV function. GAMMA.INV uses the same arguments and provides the same core functionality with improved numerical precision. See the GAMMA.INV function for more details and examples.

Notes

GAMMAINV is a legacy function. For Excel 2010 and later, use the GAMMA.INV function.
If any argument is non-numeric, GAMMAINV returns the #VALUE! error.
If probability < 0 or ≥ 1, GAMMAINV returns the #NUM! error.
If alpha ≤ 0 or beta ≤ 0, GAMMAINV returns the #NUM! error.
GAMMA.INV provides improved accuracy over the legacy GAMMAINV function.