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BETA.INV Function
Summary
The BETA.INV function calculates the inverse of the cumulative beta distribution, returning the value x where the cumulative probability matches the specified probability. This advanced statistical function is essential for project management, risk analysis, and modeling continuous variables bounded between two limits.
Syntax
BETA.INV(probability, alpha, beta, [A], [B])Parameters
| Parameter | Type | Required | Description |
|---|---|---|---|
| probability | Number |
Yes | A probability value between 0 and 1 associated with the beta distribution |
| alpha | Number |
Yes | Alpha parameter of the beta distribution (must be positive) |
| beta | Number |
Yes | Beta parameter of the beta distribution (must be positive) |
| A | Number |
No | Lower bound for the returned value (optional, defaults to 0) |
| B | Number |
No | Upper bound for the returned value (optional, defaults to 1) |
Using the BETA.INV Function
BETA.INV is primarily used in statistical analysis and project management to find critical values in beta distributions. If BETA.DIST(x, alpha, beta, TRUE, A, B) = probability, then BETA.INV(probability, alpha, beta, A, B) = x. This relationship makes it perfect for modeling task completion times with known variability.
Common BETA.INV Examples
Basic BETA.INV Calculation
=BETA.INV(0.685470581, 8, 10, 1, 3)Returns approximately 2, which is the value x where the cumulative beta probability equals 0.685470581 with alpha=8, beta=10, and bounds [1,3]
Standard Beta Distribution (A and B omitted)
=BETA.INV(0.75, 2, 5)Uses default bounds [0,1] and returns the 75th percentile of the standard beta distribution
Project Management Example
=BETA.INV(0.9, 4, 2, 10, 50)Finds the value below which 90% of outcomes fall, useful for optimistic project completion estimates
Frequently Asked Questions
Common Errors and Solutions
#NUM!
Cause: Probability ≤ 0 or > 1, or alpha ≤ 0 or beta ≤ 0
Solution: Ensure probability is between 0 and 1 (exclusive), and both alpha and beta are positive
#VALUE!
Cause: Any argument is non-numeric
Solution: Verify all inputs are valid numbers
Notes
- Precision depends on BETA.DIST accuracy
- If A ≥ B, results may be unpredictable
- Commonly used in PERT analysis for project scheduling
- Beta distribution models bounded continuous variables
Compatibility
Available in: Excel 2007, Excel 2010, Excel 2013, Excel 2016, Excel 2019, Excel 2021, Microsoft 365
Not available in: Excel 2003 and earlier
Content last reviewed: December 9, 2025
Update frequency: As needed
Excel versions tested: Excel 2007+