🔔 Normal Distribution
Probabilities under the bell curve
About this calculator
The normal distribution, the bell curve, describes everything from heights to test scores. Enter the mean and standard deviation, then a value or a range, to get exact probabilities like P(X less than a) or P(a less than X less than b).
Tip: memorize the 68-95-99.7 rule. About 68 percent of values land within one standard deviation of the mean, 95 within two, 99.7 within three.