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BETAINV Function
Summary
The BETAINV function computes the inverse of the cumulative beta distribution, finding the value x where the cumulative probability equals a given probability. Essential for statistical analysis and project planning to model completion times with variability.
Syntax
BETAINV(probability,alpha,beta,[A],[B])Parameters
| Parameter | Type | Required | Description |
|---|---|---|---|
| probability | Number |
Yes | A probability value (0 < probability < 1) associated with the beta distribution |
| alpha | Number |
Yes | Alpha parameter to the distribution (alpha > 0) |
| beta | Number |
Yes | Beta parameter to the distribution (beta > 0) |
| A | Number |
No | Optional lower bound to the interval of x (default = 0) |
| B | Number |
No | Optional upper bound to the interval of x (default = 1) |
Using the BETAINV Function
BETAINV is primarily used in statistical analysis for finding critical values in beta distributions. Common applications include project management for PERT analysis, quality control, and reliability engineering where modeling success probabilities over time intervals is needed.
Common BETAINV Examples
Standard Beta Distribution Inverse
=BETAINV(0.685470581,8,10,1,3)Returns approximately 2, the value x where BETADIST(x,8,10,TRUE,1,3) = 0.685470581
Default Bounds (0 to 1)
=BETAINV(0.75,2,5)Finds x where cumulative probability reaches 75% using standard bounds
Project Planning Example
=BETAINV(0.95,4,2,A1,B1)95th percentile completion time using optimistic (A1) and pessimistic (B1) estimates
Frequently Asked Questions
Common Errors and Solutions
#NUM!
Cause: probability ≤ 0 or > 1, or alpha ≤ 0 or beta ≤ 0
Solution: Ensure 0 < probability < 1 and alpha > 0, beta > 0
#VALUE!
Cause: Any argument is non-numeric
Solution: Verify all inputs are valid numbers
Notes
- This is a legacy function replaced by BETA.INV for improved precision
- Precision depends on BETADIST function accuracy
- Ideal for PERT analysis in project management
- If A and B omitted, uses standard beta distribution (0 to 1)
- Consider migrating to BETA.INV for new workbooks
Compatibility
Available in: Excel for Microsoft 365, Excel 2021, Excel 2019, Excel 2016, Excel 2013, Excel 2010, Excel 2007
Not available in: Excel 2003 and earlier
Content last reviewed: December 8, 2025
Update frequency: As needed
Excel versions tested: Excel for Microsoft 365, Excel for Microsoft 365 for Mac, Excel for the web, Excel 2024, Excel 2024 for Mac, Excel 2021, Excel 2021 for Mac, Excel 2019, Excel 2016