About the Normal Distribution Calculator
A free tool for finding probabilities under any normal distribution.
What it is
The Normal Distribution Calculator finds the area under the bell curve โ the probability โ below, above, between, or outside given values, using the mean and standard deviation you supply. It converts your inputs to z-scores and evaluates the standard normal cumulative distribution function.
Features
Four probability modes
Below, above, between, and outside a value or range.
Visual curve
See the bell curve with the relevant area shaded.
Z-scores shown
See the exact z-score computed for each boundary.
Instant, private
Runs entirely in your browser. No data is sent anywhere.