Statistics
Math and statistics calculators with step-by-step formulas and worked examples for students and professionals.
Mean Calculator
Calculate the arithmetic, geometric and harmonic means of a data set, with formulas, a worked example, and guidance on when each mean is appropriate.
Median Calculator
Find the median, mode and range of a data set with worked examples. Handles even-sized lists and multiple modes, and explains median vs mean for skewed data.
Standard Deviation Calculator
Calculate sample and population standard deviation, variance and mean for any data set, with the n-1 vs n distinction explained and a worked example.
Probability Calculator
Calculate the probability of two independent events: both occurring, either occurring, neither occurring, and the complement — with formulas and examples.
Sample Size Calculator
Calculate the survey sample size you need using Cochran's formula with finite population correction, at 90%, 95% or 99% confidence and your margin of error.
Confidence Interval Calculator
Calculate a z-based confidence interval for a mean from the sample mean, standard deviation and size, with the margin of error and standard error shown.
Z-Score Calculator
Calculate a z-score from a value, mean and standard deviation, plus the normal-distribution percentile and the share of values above. Worked example inside.