Standard Deviation Calculator
Measure how spread out your numbers are.
What would you like to do next?
Measure the spread of your data
Standard deviation tells you how far, on average, the values in a data set sit from their mean. A small figure means the numbers cluster tightly; a large one means they are widely scattered. Enter at least two numbers and this tool reports the mean, the sample standard deviation, the population standard deviation and the sample variance. Pick the sample version when your data is a subset, and the population version when it covers the whole group.
Sample or population?
Sample standard deviation divides by one fewer than the count, which corrects for estimating spread from a subset rather than the entire population.
Frequently asked questions
Sample or population — which should I use?
The sample version divides the squared differences by the count minus one, giving an unbiased estimate from a subset. The population version divides by the full count.
How many numbers do I need?
At least two. With a single value there is no spread to measure.