Statistics100% Free9 tools

Free Statistics and Probability Calculators

Plan surveys, measure uncertainty, fit lines, test correlation and work out probabilities. Each calculator shows its working, and everything runs in your browser.

Surveys and samples

Sample Size CalculatorSurvey sample size for a confidence level and margin of error. Margin of Error CalculatorMargin of error and range for a survey percentage. Confidence Interval CalculatorConfidence interval for a mean from data or summary numbers.

Data analysis

Linear Regression CalculatorBest-fit line, R squared and predictions from x and y pairs. Correlation Coefficient CalculatorPearson and Spearman correlation with strength and p-value. Percentile CalculatorPercentile rank, percentile value and quartiles for a list.

Probability

Probability CalculatorCombine two independent events and repeated trials. Binomial Probability CalculatorBinomial probabilities for n trials, success chance p and count k. Normal Distribution CalculatorNormal probabilities below, above, between, and inverse.

How These Statistics Tools Work

Every calculator on this site runs in your browser with JavaScript. The data you enter is processed on your own device and is not uploaded or stored. No outside service is used. Probabilities come from standard numerical methods such as the error function, the log-gamma function and the incomplete beta function.

Which Tool Should I Use?

Surveys: the sample size calculator, the margin of error calculator and the confidence interval calculator.
Relationships: the linear regression calculator and the correlation calculator.
Probability: the probability calculator, the binomial calculator and the normal distribution calculator.
Describing data: the percentile calculator.

More free tools: math calculators (including mean, standard deviation and z-scores), random generators and finance and health calculators. For theory, see the Wikipedia article on statistics.