Statistics calculator library

Statistics Calculators

Free online probability and distribution calculators with formulas, worked examples, step-by-step calculations and clear explanations.

Probability distribution calculators

P(X=x), cumulative, range, inverse, mean, variance and standard deviation.

Z-scores, tails, ranges, percentiles and inverse normal values.

Exact, cumulative, tail, range and no-event probabilities.

Choose a distribution

Binomial: fixed independent trials with two outcomes and the same success probability.

Normal: a continuous bell-shaped model described by a mean and standard deviation.

Poisson: event counts in a fixed interval described by an average rate.