GAMMA.DIST function
Returns the gamma distribution. You can use this function to study variables that may have a skewed distribution. The gamma distribution is commonly used in queuing analysis.
Syntax
GAMMA.DIST(x,alpha,beta,cumulative)
The GAMMA.DIST function syntax has the following arguments:

X Required. The value at which you want to evaluate the distribution.

Alpha Required. A parameter to the distribution.

Beta Required. A parameter to the distribution. If beta = 1, GAMMA.DIST returns the standard gamma distribution.

Cumulative Required. A logical value that determines the form of the function. If cumulative is TRUE, GAMMA.DIST returns the cumulative distribution function; if FALSE, it returns the probability density function.
Remarks

If x, alpha, or beta is nonnumeric, GAMMA.DIST returns the #VALUE! error value.

If x < 0, GAMMA.DIST returns the #NUM! error value.

If alpha ≤ 0 or if beta ≤ 0, GAMMA.DIST returns the #NUM! error value.

The equation for the gamma probability density function is:
The standard gamma probability density function is:

When alpha = 1, GAMMA.DIST returns the exponential distribution with:

For a positive integer n, when alpha = n/2, beta = 2, and cumulative = TRUE, GAMMA.DIST returns (1  CHISQ.DIST.RT(x)) with n degrees of freedom.

When alpha is a positive integer, GAMMA.DIST is also known as the Erlang distribution.
Example
The example may be easier to understand if you copy it to a blank worksheet.
How do I copy an example?

Select the example in this article. If you are copying the example in Excel Web App, copy and paste one cell at a time.Important Do not select the row or column headers.
Selecting an example from Help

Press CTRL+C.

Create a blank workbook or worksheet.

In the worksheet, select cell A1, and press CTRL+V. If you are working in Excel Web App, repeat copying and pasting for each cell in the example.

Important For the example to work properly, you must paste it into cell A1 of the worksheet.

To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.

After you copy the example to a blank worksheet, you can adapt it to suit your needs.

