DocomintStandard Deviation Calculator
Calculate sample and population standard deviation and variance for a set of numbers.
Standard deviation measures how spread out a data set is around its mean — a small value means the numbers cluster tightly, a large one means they're scattered. This computes both the sample formula (dividing by n-1, the one used when your numbers are a subset of a bigger population — the common case for survey data or a class's test scores) and the population formula (dividing by n, for when your list is the entire population you care about), since which one is "correct" depends on which situation you're in.
Example: Seven data points — 4, 8, 6, 5, 3, 9, 7 — have a mean of 6 and a sample standard deviation of about 2.16, meaning most values sit within roughly 2 points of the mean.
How it works
- Paste a list of numbers, separated by commas or one per line
- Press Calculate
- Both sample and population standard deviation appear instantly, computed on your device
Frequently asked questions
What's the difference between population and sample standard deviation?
Population standard deviation (dividing by n) is used when your data is the entire group you care about. Sample standard deviation (dividing by n−1) is used when your data is a subset used to estimate a larger population — the more common case for survey or experimental data, and why it's shown first here.
What does a high standard deviation mean?
It means the values are spread widely around the mean rather than clustered close to it. A low standard deviation means the values are consistent and close together; a high one means more variability or volatility in the data set.
Is my numbers uploaded anywhere?
No — Standard Deviation Calculator runs entirely in your browser using JavaScript/WebAssembly. Your numbers is never sent to a server.