Probability Calculators

Apply Bayes' theorem to conditional probability problems. Enter prior probability and likelihoods — see posterior probability with tree diagram. Free.

Calculate the probability two people share a birthday in a group. Enter group size — see exact probability with formula and 50% threshold. Free.

Probability of dice outcomes for any number of dice. Step-by-step solution with formula, example dataset and interpretation guide.

Calculate the odds of winning any lottery. Enter pool size and picks — see probability as fraction, percentage, and 1-in-N odds. Free.

Probability of drawing specific cards from a deck. Step-by-step solution with formula, example dataset and interpretation guide.

Calculate expected value for any probability distribution. Enter outcomes and probabilities — see E(X), variance, and standard deviation. Free.

Convert between probability and odds. Fast and accurate result with formula, step-by-step method and unit overview. Free tool.

Find the probability of winning in the gambler's ruin problem. Enter starting stake, target, and win probability — see exact ruin probability. Free.