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GAMMADIST Function
Summary
The GAMMADIST function calculates the gamma distribution, ideal for analyzing skewed data distributions commonly found in queuing theory, reliability analysis, and process modeling. Note: This legacy function is replaced by GAMMA.DIST for enhanced precision.
Syntax
GAMMADIST(x, alpha, beta, cumulative)Parameters
| Parameter | Type | Required | Description |
|---|---|---|---|
| x | Number |
Yes | The value at which you want to evaluate the distribution (x ≥ 0) |
| alpha | Number |
Yes | Shape parameter to the gamma distribution (alpha > 0) |
| beta | Number |
Yes | Scale parameter to the gamma distribution (beta > 0). When beta=1, returns standard gamma distribution. |
| cumulative | Boolean |
Yes | Logical value: TRUE returns cumulative distribution, FALSE returns probability density |
Using the GAMMADIST Function
GAMMADIST is primarily used in advanced statistical analysis for modeling continuous variables with right-skewed distributions, such as time between events in Poisson processes or equipment failure times.
Common GAMMADIST Examples
Probability Density Calculation
=GAMMADIST(10,9,2,FALSE)Returns the probability density at x=10 for alpha=9, beta=2 (result: approximately 0.0326)
Cumulative Distribution
=GAMMADIST(10,9,2,TRUE)Returns the cumulative probability up to x=10 for alpha=9, beta=2 (result: approximately 0.0681)
Exponential Distribution (alpha=1)
=GAMMADIST(5,1,2,FALSE)Calculates exponential distribution density with mean=2 at x=5
Frequently Asked Questions
Common Errors and Solutions
#NUM!
Cause: x < 0, alpha ≤ 0, or beta ≤ 0
Solution: Ensure x ≥ 0, alpha > 0, and beta > 0
#VALUE!
Cause: Non-numeric input for x, alpha, beta
Solution: Verify all numeric parameters are valid numbers
Notes
- Replaced by GAMMA.DIST function for improved accuracy
- When alpha=1, returns exponential distribution
- For alpha=n/2, beta=2, cumulative=TRUE: equivalent to 1-CHIDIST(x) with n degrees of freedom
- Critical for queuing theory and reliability analysis
Compatibility
Available in: Excel 2003, Excel 2007, Excel 2010, Excel 2013, Excel 2016
Not available in: Excel 2019, Excel 2021, Microsoft 365 (use GAMMA.DIST)
Content last reviewed: December 9, 2025
Update frequency: As needed
Excel versions tested: Excel 2003, Excel 2007, Excel 2010, Excel 2013, Excel 2016