In MS Excel, Gamma distribution can be easily calculated by using GAMMA.DIST function. This function is available from MS Excel 2010 onwards. For previous version there is GAMMADIST function (without a dot between).

=GAMMA.DIST (x, alpha, beta, cumulative)

- X (Required)– The value at which gamma function would be evaluated
- Alpha / α (Required) – A parameter of the distribution used for determining the shape.
- beta / β (Required) – A parameter of the distribution for determining the rate

α and β are both must be greater than 1.

When α = 1, it corresponds to exponential distribution.

When β = 1, it corresponds to the standard gamma distribution.

Cumulative (Required) - A logical value that determines the form of the function.

Cumulative =TRUE, it returns the cumulative distribution function

Cumulative =FALSE, it returns the probability density function.

Go to an empty cell and type =GAMMA.DIST

- Type the value where we need to find probability. This gives us the value of x. In the example below, x= 5
- Type the alpha and beta value as the next parameters, both comma separated. Here, α = 4 & β = 3
- Type
**True**for cumulative distribution. Type**False**for probability density function.

**=GAMMA.DIST(5, 4, 3, TRUE)**

Result: 0.088267

**=GAMMA.DIST(5, 4, 3, False)**

Result: 0.048579

Cumulative Distribution function (CDF)

Formula: **=GAMMA.DIST(D16, 4, 3, TRUE) **

Probability Density function (PDF)

Formula: **=GAMMA.DIST(D16, 4, 3, FALSE)**

- #NUM! – Occurs under following scenarios:

Value of x < 0

Value of α ≤ 0 or β ≤ 0

- #VALUE! – Occurs under following scenarios:

Any of the arguments – x, alpha, beta are non-numeric in nature

The fourth parameter is not TRUE OR FALSE, unrecognized

Further reading: Distribution chart