Standard Deviation Calculator
Get the standard deviation, variance and mean of a set of numbers instantly.
How to use the Standard Deviation Calculator
- Type or paste your numbers, separated by commas or spaces.
- Choose “Sample” if the data is a subset, or “Population” for the whole set.
- Read off the standard deviation, variance and mean.
σ = √( Σ(xᵢ − mean)² ÷ N ). Use N − 1 for a sample.
About the Standard Deviation Calculator
Standard deviation measures how spread out a set of numbers is around their average. A small value means the numbers cluster tightly around the mean; a large one means they’re scattered widely. It’s one of the most-used measures in statistics, finance and science.
The calculator also shows the variance (standard deviation squared) and the mean. The key choice is sample vs population: use sample (dividing by n − 1) when your numbers are a subset of a larger group, and population (dividing by n) when they’re the entire group.
Use it to compare consistency between data sets, measure investment volatility, or check quality-control spread — anywhere the average alone doesn’t tell the whole story.
Frequently asked questions
Sample or population — which do I pick?
If your numbers are all the data there is, use population. If they’re a sample used to estimate a bigger group, use sample (n − 1), which corrects for the smaller size.
How is it different from variance?
Variance is the average of the squared differences from the mean; standard deviation is its square root, which brings the figure back into the original units.
Can I use decimals and negatives?
Yes. Enter any real numbers separated by commas or spaces — decimals and negative values are all handled.