Standard Deviation Calculator

The Standard Deviation Calculator turns a list of numbers into a full statistical summary: count, sum, mean, median, minimum, maximum, and both the population and sample variance and standard deviation.

Paste or type your values separated by spaces or commas and every measure is computed at once.

Standard deviation tells you how spread out a dataset is around its average — a small value means the numbers cluster tightly, a large one means they vary widely.

It is one of the most useful descriptive statistics, but it comes in two flavours that are easy to confuse.

The population version divides by the number of values and applies when your data is the entire group; the sample version divides by one less (Bessel’s correction) and applies when your data is a sample meant to estimate a larger population.

This tool shows both, clearly labelled, so you do not have to remember which formula your situation calls for.

It also gives you the supporting measures — the mean and median to describe the centre, the range from minimum to maximum, and the variance that the standard deviation is the square root of.

Results are rounded to remove floating-point noise, an empty list is rejected with a clear message, and every figure has a copy button.

The whole calculation runs locally in your browser.