Probability, permutation, combination, and Bayes theorem calculators. Browse our free probability tools below — all calculators are instant, accurate, and require no sign-up.
6-Sided Dice Probability Calculator — Calculate exact probabilities for rolling 6-sided dice — sums, specific values, at-least-one conditions, and repeated trial outcomes with distribution tables.
AND Probability Calculator — Calculate the probability of two or three events both occurring — independent or dependent — with breakdowns, odds, and repeated trial analysis.
Bayes' Theorem Calculator — Apply Bayes' theorem to update probabilities with new evidence — compute posterior probability, likelihood ratios, and confusion matrices for medical tests.
Beta Distribution Calculator — Compute PDF, CDF, mean, mode, variance, and percentiles for the beta distribution with interactive shape parameter presets and visual curve.
Binomial Distribution Calculator — Calculate binomial probabilities, cumulative distribution, mean, variance, and confidence intervals for any number of trials and success probability.
Birthday Paradox Calculator — Calculate the surprising probability that two or more people in a group share a birthday — with tables, visual bars, and customizable year length.
Central Limit Theorem Calculator — Explore the Central Limit Theorem — compute standard error, z-scores, confidence intervals, and see how sample size affects the sampling distribution.
Coin Flip Probability Calculator — Calculate the probability of getting a specific number of heads or tails in coin flips — exact, cumulative, streaks, and distribution tables.
Conditional Probability Calculator — Calculate P(A|B) and P(B|A) from joint, marginal, or conditional inputs — with contingency tables, independence tests, and lift analysis.
Exponential Distribution Calculator — Compute PDF, CDF, percentiles, and reliability statistics for the exponential distribution with interactive rate parameter and visual density curve.
Hypergeometric Distribution Calculator — Calculate exact hypergeometric probabilities for sampling without replacement, with PMF, CDF, distribution tables, and binomial approximation comparison.
Implied Probability Calculator — Convert American, decimal, and fractional betting odds to implied probability with EV analysis, Kelly criterion, edge visualization, and vig breakdown.
Joint Probability Calculator — Calculate joint, union, and conditional probabilities for two events, with contingency tables, Venn diagram visualization, lift analysis, and repeated-event chains.
Lognormal Distribution Calculator — Compute PDF, CDF, percentiles, and moments for the lognormal distribution with interactive density curve, percentile table, and properties reference.
Monty Hall Problem Calculator — Explore the Monty Hall problem with analytical probabilities and Monte Carlo simulation for 3+ doors, variable reveals, and strategy comparison visuals.
Negative Binomial Distribution Calculator — Calculate negative binomial probabilities — failures before the r-th success — with full distribution table, visual chart, and parameter sensitivity analysis.
OR Probability Calculator — Calculate P(A or B) for mutually exclusive, non-exclusive, and three-event scenarios with stacked probability bars, comparison tables, and repeated-trial analysis.
Normal Distribution & Sampling Calculator — Compute normal distribution probabilities, z-scores, and sampling distributions with visual comparison of population vs sample mean curves and confidence intervals.
Probability Fraction Calculator — Convert probability fractions to decimals, percentages, and odds. Simplify fractions, combine probabilities, compute binomial distribution over trials, and view equivalent fractions.
Post-Test Probability Calculator — Calculate post-test probability from sensitivity, specificity, and prevalence with likelihood ratios, confusion matrix, sequential testing, and PPV/NPV sensitivity analysis.
Probability of Three Events Calculator — Calculate combined probability of three events using inclusion-exclusion. Supports independent and dependent events with Venn diagram regions, conditional probabilities, and repeated trials.
Two Dice Probability Calculator — Calculate two-dice probabilities for sums, doubles, products, and differences. View complete sum distribution, outcome grid, cumulative probabilities, and custom-sided dice support.
Uniform Distribution Calculator — Calculate probabilities, percentiles, and statistics for continuous and discrete uniform distributions. Includes PDF/CDF visualization, quantile table, order statistics, and sampling distribution.
Venn Diagram Calculator — Calculate Venn diagram regions for 2 or 3 sets. Find unions, intersections, complements, conditional probabilities, Jaccard similarity, and all exclusive regions with visual diagrams.
Weibull Distribution Calculator — Calculate Weibull distribution PDF, CDF, survival, hazard rate, MTTF, percentiles, and B-life. Supports reliability analysis with shape and scale parameters plus mission time planning.