Standard Deviation Calculator
Paste numbers to get the mean, variance, and standard deviation (population or sample).
Measure the spread of your data
The mean tells you the centre of a data set, but not how tightly the values gather around it — that is what standard deviation captures. This calculator reports the mean, the variance, and the standard deviation for any list of numbers.
For 2, 4, 4, 4, 5, 5, 7, 9 the mean is 5 and the population standard deviation is 2. A larger figure would mean the same average hides much wider scatter, which changes how you interpret it.
Population or sample, kept private
Choose population when your numbers are the whole group or sample when they estimate a larger one; the sample option divides by n−1. All math runs in your browser.
Frequently Asked Questions
What does standard deviation measure?
How spread out the numbers are around the mean. A small value means the data clusters tightly; a large one means it is widely scattered.
Population vs sample — which do I pick?
Use population when your numbers are the entire group, and sample when they are a subset you are using to estimate a larger population. Sample divides by n−1.
How is it related to variance?
Standard deviation is the square root of the variance, which brings the spread back into the same units as your original data.
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