All calculators
41 free calculators, each with step-by-step working, a worked example and answers to the questions students ask most. Plus the all-in-one statistics calculator on the home page.
Describe a data set
- Standard Deviation CalculatorSample s and population σ, with the full deviation table.
- Variance Calculators² and σ², showing the sum of squared deviations.
- Mean, Median, Mode CalculatorAll four averages-and-spread basics, sorted and explained.
- Mean CalculatorSum ÷ count, with the working.
- Range CalculatorMax − min, plus midrange.
- Weighted Average CalculatorGrades by percentage, credits or counts.
- Geometric Mean Calculatornth root of the product; average growth rates.
- Median CalculatorMiddle value of the sorted list, odd or even n.
- Mode CalculatorMost frequent value(s), with a frequency table.
- Relative Frequency CalculatorFrequency, relative and cumulative frequency table.
- Mean Absolute Deviation CalculatorAverage distance from the mean, |x − x̄|.
- Sum of Squares CalculatorSS = Σ(x − x̄)², the heart of variance.
- Skewness CalculatorIs the data lopsided or heavy-tailed?
- Five Number Summary CalculatorMin, Q1, median, Q3, max and a box plot.
- Interquartile Range CalculatorQ1, Q3, IQR, five-number summary and a box plot.
- Outlier CalculatorTukey fences: Q1 − 1.5·IQR and Q3 + 1.5·IQR.
- Percentile CalculatorValue at the kth percentile, or a value’s rank.
- Standard Error CalculatorSE = s ÷ √n from data or summary numbers.
- Coefficient of Variation CalculatorCV = s ÷ mean, also called RSD.
Distributions & tables
- Z-Score Calculatorz = (x − μ) ÷ σ plus the area under the curve.
- Z-Score TableFull left-tail table, −3.49 to 3.49, with lookup.
- Normal Distribution CalculatorAreas under any bell curve, and invNorm.
- Empirical Rule Calculatorμ ± 1, 2, 3σ ranges on a bell curve.
- Expected Value CalculatorE(X) = Σ x·P(x), with variance.
- Binomial Distribution CalculatorExactly, at most, at least k successes — with a histogram.
Tests & estimation
- P-Value CalculatorFrom z, t, χ² or F statistics; one or two tails.
- Confidence Interval CalculatorMean (z or t) and proportion intervals, with steps.
- Margin of Error CalculatorThe ± in poll results, for proportions and means.
- Sample Size CalculatorHow many responses for a given ± and confidence.
- T-Test CalculatorOne-sample, Welch/pooled two-sample, and paired.
- Chi-Square CalculatorGoodness of fit and contingency tables.
- Linear Regression CalculatorLeast-squares line, r², residuals and predictions.
- Correlation Coefficient CalculatorPearson r, r² and its t-test.