18 free tools — instant, accurate, and no sign-up required.
Mean, median, mode, standard deviation, variance, IQR, skewness, kurtosis, and more.
PDF, CDF, z-scores, and tail probabilities for any normal distribution.
Convert a value to a z-score, find its percentile, and tail probabilities.
One-sample, two-sample (independent), and paired t-tests with interpretation.
Goodness of fit and independence tests, with Cramér's V effect size.
Compare means across three or more groups. F-statistic and p-value.
Non-parametric alternative to the independent t-test for skewed or ordinal data.
Compare two proportions or conversion rates — ideal for A/B tests.
CI for a population mean (t) or proportion (z), at any confidence level.
Required n for estimating a mean or proportion at a target margin of error.
Cohen's d and Hedges' g for two-sample, one-sample, and paired designs.
Pearson and Spearman coefficients with p-value, 95% CI, and scatter plot.
Slope, intercept, R², residuals, and a fitted regression line chart.
Exact and cumulative binomial probabilities, with distribution table and chart.
Probability of k events given an average rate λ, with table and PMF chart.
Two events — AND, OR, conditional, and "at least one" — with a live Venn diagram.
Compute nPr, nCr, and factorials exactly, with a binomial-coefficient chart.
Drag sliders and watch the normal, binomial, Poisson, and t distributions change live.
Drag sliders and watch the normal, binomial, Poisson, and t distributions change live.
Pick any population, draw samples, and watch the sample mean become a bell curve.
A stats game: see a scatterplot, guess r, get scored. Build real intuition for correlation.
Answer a few questions and get the right statistical test with a link to its calculator.
Looking for critical values? Browse the statistical tables →
New to statistics? Start with the plain-English guides →
Revising? Grab the statistics formulas cheat sheet →
Not sure which test you need? Try the interactive test chooser →