Math & Tools
Statistics & Probability Calculators
Averages, spread, probability, combinatorics and sampling. Free calculators with formulas and worked examples.
Counting
Probability
Probability Calculator (Two Events)Enter the probability of events A and B (as percentages) to see combined probabilities for independent events.Bayes' Theorem CalculatorFind the probability that a condition is true given a positive test, using Bayes' theorem.Coin Flip Probability CalculatorHow likely is it to get k heads in n flips?Expected Value CalculatorFind the average result of a bet or decision with up to three outcomes.Odds ConverterConvert a probability into the common odds formats.Birthday Paradox CalculatorHow many people do you need before two probably share a birthday?Lottery Odds CalculatorFind the jackpot odds of a pick-k-from-n lottery.Probability of At Least One CalculatorEnter the chance per try and the number of tries.Dice Probability Calculator (Sum of Several Dice)Choose the dice and the total you are interested in.
Distributions
Binomial Distribution CalculatorCalculate binomial probabilities for n trials with success probability p.Poisson Distribution CalculatorFind the probability of k events in an interval when events happen at an average rate λ.Normal Distribution CalculatorEnter the mean, standard deviation and a value x to find its z-score and probabilities.Z-Score CalculatorSee how many standard deviations a value is from the mean.Hypergeometric Probability CalculatorDraw n items without replacement from a population containing K successes.Geometric Distribution CalculatorHow many attempts until the first success?Exponential Distribution CalculatorEnter the rate (or the mean time between events) and a value of x.
Inference
Confidence Interval Calculator (Mean)Estimate a range likely to contain the true mean, using the normal (z) approximation.Margin of Error Calculator (Proportion)Find the margin of error for a poll or survey result.Sample Size CalculatorHow many people do you need to survey?Standard Error CalculatorFind the standard error from a standard deviation and sample size.
Descriptive statistics
Coefficient of Variation CalculatorCompare variability between data sets with different units or scales.Mean, Median and Mode CalculatorPaste or type your numbers to get the mean, median, mode and range at once.Average CalculatorPaste your numbers to find their average instantly.Standard Deviation CalculatorPaste your data to get the standard deviation, variance and mean, for a sample or a whole population.Variance CalculatorPaste your numbers to get the sample and population variance side by side.Quartile and Interquartile Range (IQR) CalculatorPaste your data to get Q1, the median, Q3, the IQR and the five-number summary.Outlier Calculator (IQR Fences and Box Plot)Paste your data to find the box-plot fences and count the outliers.Percentile Calculator (From Data)Paste your data, choose a percentile, and see the value at that percentile and where any score ranks.Weighted Average CalculatorEnter values and their weights in the same order to get the weighted average.Geometric Mean CalculatorPaste positive numbers to get their geometric mean, with the arithmetic and harmonic means for comparison.Harmonic Mean CalculatorPaste positive rates to get their harmonic mean.Skewness and Kurtosis CalculatorPaste your data to see whether it is skewed and how heavy its tails are.Mean Absolute Deviation (MAD) CalculatorPaste your data to get the mean absolute deviation around the mean.Sum Calculator (Add a List of Numbers)Paste a list or column of numbers to add them all up.Root Mean Square (RMS) CalculatorPaste your values to get their root mean square.
Health statistics
Correlation and regression
Correlation Coefficient Calculator (Pearson r)Enter paired X and Y values to measure how strongly they move together.Linear Regression Calculator (Line of Best Fit)Enter X and Y values to get the line of best fit and predict Y for a new X.Covariance CalculatorEnter paired X and Y values to get their covariance.
Hypothesis tests
T-Test Calculator (Two Samples, Welch or Pooled)Paste the two samples and choose the test and alternative hypothesis.One-Way ANOVA Calculator (Two or Three Groups)Paste each group's values (leave the third group empty for two groups).Chi-Square Goodness of Fit CalculatorEnter the observed counts and the expected counts or proportions, in the same order.P-Value Calculator (z, t, Chi-Square and F)Choose the test statistic's distribution and enter its value and degrees of freedom.
Effect size
About these calculators
Describe a data set, count arrangements and work out probabilities. These calculators cover the standard measures of centre and spread, counting rules and common distributions, and explain the assumptions behind each formula.
Each calculator explains its formula, includes a worked example and lists its sources. Read how we check them on our editorial policy page, or browse all calculators.
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Please note: TheCalcTools gives general estimates for information and education. It is not financial, medical, legal or tax advice, and results should be checked before you make a decision. See our disclaimer and about page.