Statistics Calculators

Descriptive statistics, probability, hypothesis tests and sample-size tools.

All statistics calculators

• Bayes Theorem CalculatorEnter how common event A is, how often B shows up when A is true, and how often B shows up when A is false. The calculator returns the updated probability of A after you observe B, and after you do not.
• Binomial Distribution CalculatorEnter the chance of success on a single trial, how many trials are run and how many successes you are asking about. The result is the exact probability together with four cumulative ones, and a second tab works backwards to find the trials required.
• Chi-Square CalculatorPaste a table of counts, or a column of observed counts next to expected frequencies, and choose the type of test. The result is the chi-square statistic, its p-value and the degrees of freedom, with a warning when the data are too sparse.
• Chi-Square to P-value CalculatorType the chi-square value from your test and its degrees of freedom to get the p-value. It is the quickest way to finish a test when you already have the statistic but not the probability.
• Coefficient of Variation CalculatorThe coefficient of variation expresses spread as a fraction of the mean, so variability can be compared across data sets with different units or scales. Enter summary values, paste raw data, or give a proportion and a sample size.
• Combination CalculatorEnter how many items you can choose from and how many you will pick, and the calculator returns the number of different selections. Tick the repetition box when the same kind of item may be picked more than once.
• Confidence Interval CalculatorGet a confidence interval for a single average, or for the gap between two groups measured as means or proportions, in absolute or relative terms. Choose your confidence level and read both the two-sided and one-sided bounds.
• Correlation Coefficient CalculatorPaste paired X and Y values, choose Pearson, Spearman or Kendall, and get the coefficient together with its Z score, one-sided p-value, confidence intervals and the least-squares line.
• Covariance CalculatorPaste your X and Y values, one pair per row, and the calculator returns the sample covariance, the population covariance and the mean of each variable. Add a third column of weights to get the weighted version.
• Critical Value CalculatorChoose the distribution of your test statistic, enter the significance level and the degrees of freedom, and read off the critical value and the rejection region. The guide shows how to use the result and lists common table values.
• Dice Probability CalculatorPick the die, the number of dice and the outcome you care about, such as a sum of at least 10 or at least one 6. You get the exact chance as a decimal and a percentage, together with the odds written as 1 in N.
• Error Function CalculatorEnter x to get erf(x) and erfc(x), or enter y between -1 and 1 to get the inverse functions. Choose how many decimals you want to see, up to 25; at most 15 significant digits are printed.
• Hazard Ratio CalculatorPaste one row per time period with the events and the number at risk in a treatment and a control group. The calculator returns the average hazard ratio, its confidence intervals at the level you choose, the chi-square statistic and the p-value.
• Normal Distribution CalculatorThree tools in one: turn a raw score into tail probabilities, turn a probability into a Z score, or find the cut-off value that has a given probability below it. Set the mean and standard deviation, or leave the standard normal defaults.
• Normality CalculatorPaste a column of numbers and run six normality tests in one go. Each result shows a p-value and its test statistic, together with the mean, range and standard deviation of your data.
• Odds Ratio CalculatorEnter the number of events and non-events in an exposed group and a control group to get the odds ratio, its confidence intervals at the level you choose, and a p-value for the null of no association.
• P-value CalculatorCompare two groups, such as a control and a variant, and find out how likely a difference this large would be if there were no real effect. Enter proportions or means, pick a Z-test or a T-test, and read off the p-value and significance level.
• P-value to Z-score CalculatorEnter a p-value, choose whether it is one-tailed or two-tailed, and the calculator returns the Z-score that corresponds to it on the standard normal curve.
• Percent Error CalculatorType the value you measured and the value you expected, and the calculator returns the percent error. A positive result means the measurement came out too high, a negative one too low.
• Permutations CalculatorEnter how many items you can choose from and how many places you are filling, and the calculator counts the different ordered arrangements. Tick the repetition box when the same item may be used more than once.
• Power & Sample Size CalculatorWork out how many observations a test needs to detect an effect of a given size, or how much power a planned sample size gives you. Choose the design, enter the baseline and the minimum effect of interest, and read off the result.
• Random Number Generator 🎲Set the lowest and highest value, say how many numbers you want, and the generator draws them at random. Every number in the range is equally likely on every draw.
• Relative Risk CalculatorEnter how many people in an exposed group and in a control group did and did not experience the outcome. You get the risk ratio, two-sided and one-sided confidence intervals, a one-sided p-value, the z-score and the number needed to treat.
• Sample Ratio Mismatch CalculatorPaste the number of users, sessions or visits in each test group and say how traffic was meant to be split. The calculator runs a chi-square goodness-of-fit test and tells you whether the observed split is plausible.
• Severity CalculatorEnter the data from a two-group test and the value you want to make a claim about. The calculator returns the severity of that claim, together with the p-value, the test statistic and the significance level.
• Standard Deviation CalculatorPaste your numbers, choose sample or population, and get the standard deviation with the variance, mean, standard error of the mean, range and count. A second mode handles proportions and rates.
• Variance CalculatorEnter your numbers, choose sample or population, and read off the variance along with the standard deviation, mean, standard error and count. A proportion mode covers yes/no outcomes.
• Z Score CalculatorEnter a raw score with the mean and standard deviation of its distribution to get the z score and the areas above, below and outside it. Or enter a probability to get the matching critical z score.
• Z-score to P-value CalculatorEnter a Z-score, choose a one-tailed or two-tailed test and get the matching p-value from the standard normal distribution. The guide explains how to read the number.