The Excel GAMMADIST function returns the gamma distribution, used to model waiting times and skewed positive data. It is a legacy function — Microsoft replaced it in Excel 2010 with GAMMA.DIST, which takes the same arguments.
Syntax
| Argument | Description | |
|---|---|---|
x | Required | The value at which to evaluate the distribution (must be ≥ 0). |
alpha | Required | The shape parameter of the distribution (must be > 0). |
beta | Required | The scale parameter (must be > 0). When beta = 1, GAMMADIST returns the standard gamma distribution. |
cumulative | Required | TRUE for the cumulative distribution function (CDF); FALSE for the probability density function (PDF). |
How to use it
GAMMADIST evaluates the gamma distribution at x for a given shape (alpha) and scale (beta). The fourth argument switches between the cumulative probability and the density.
The inverse function, GAMMAINV (modern GAMMA.INV), takes a probability and returns the matching x. All arguments must be numeric; alpha and beta must be positive and x non-negative.
Use GAMMA.DIST in Excel 2010 and later. GAMMADIST still works for backward compatibility, but Microsoft recommends GAMMA.DIST, which has identical arguments and improved accuracy. New workbooks should use the modern name.
Try it: interactive demo
Pick a GAMMADIST example to see the formula and its result.
Practice workbook
Frequently asked questions
Should I use GAMMADIST or GAMMA.DIST?
GAMMA.DIST in Excel 2010 or later — it takes the same four arguments and is the supported version. GAMMADIST is kept only so older workbooks keep working.What is the difference between the cumulative and density results?
cumulative = TRUE you get the probability that the variable is at or below x (the CDF). With FALSE you get the height of the probability density curve at x (the PDF).What does the beta argument do?
beta is the scale parameter. Setting beta = 1 gives the standard gamma distribution; larger values stretch the distribution along the x-axis.Why does GAMMADIST return an error?
x ≥ 0 and both alpha and beta strictly greater than 0. Negative or zero parameters, or non-numeric arguments, produce an error.Master functions like this in one day
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