How to Use the Beta Distribution with BETA.DIST in Excel

Use BETA.DIST to model percentages and bounded durations — sprint completion rates and project schedules.

You will learn to

• Find the chance a percentage is below a level
• Find the chance it is above a level
• Use custom lower and upper bounds

How it works

The beta distribution describes values that live between two limits — most often a percentage between 0 and 1, like a completion rate or a conversion rate. Its two shape parameters set where the curve peaks: alpha 8 and beta 3 centre it around 73%.

BETA.DIST(x,alpha,beta,TRUE) returns the chance of x or less. Add the optional A and B arguments to stretch the curve over any range, such as a job that will take between 20 and 50 days. That makes it a natural fit for PERT-style schedule estimates.

=BETA.DIST(0.6,8,3,TRUE)