Standard Deviation Calculator

About this calculator

This calculator finds the sample standard deviation (using Bessel's correction, dividing by n−1) and the population standard deviation (dividing by n) of a list of numbers, along with the variance and arithmetic mean. Standard deviation measures how spread out the values are around the mean — a low value means the data clusters tightly, a high value means it's scattered.

Statisticians, researchers, teachers, and students use it constantly: in quality control to check manufacturing consistency, in finance to measure volatility, and in science to report the uncertainty of measurements. Use the sample formula when your numbers are a subset drawn from a larger population; use the population formula when your list is the entire population itself.