Everyday utility

Standard Deviation Calculator

Calculate population and sample standard deviation, variance, and mean for a set of numbers. Use this Data and utilities tool to enter your numbers, review the result, and understand the key assumptions before making the next decision.

What you get
A focused calculator, clear explanation, common questions, and useful next tools.
Quick intro
Calculator
Result
Explanation
Common questions
Related tools

Calculator tool

How this calculator works
The result depends on the numbers you enter and the assumptions shown below.

Standard deviation measures how spread out numbers are from the mean. Population SD uses N; sample SD uses N−1 (Bessel's correction). A small SD means data is clustered near the mean.

Review the inputs carefully and treat the output as an estimate. For decisions involving money, taxes, health, law, or security, compare the result with trusted professional guidance when needed.

Frequently asked questions

When do I use sample vs. population standard deviation?

Use population SD when you have data for an entire population. Use sample SD (with N−1) when your data is a sample drawn from a larger population — it corrects for bias.