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Standard Deviation Calculator
Standard deviation says how far a typical value sits from the mean, which is what tells you whether an average is trustworthy. Paste your data, choose sample or population, and read the deviation, the variance and the standard error together.
How to use it
- Paste the numbers in any layout.
- Pick sample if the data is part of a larger group, or population if it is everything.
- Read the standard deviation, with variance, mean and standard error underneath.
Examples
- 4, 8, 15, 16, 23, 42 → sample deviation about 13.3 around a mean of 18.
- Two data sets can share a mean of 50 while one has a deviation of 2 and the other of 25 — the average alone hides that.
- Test scores with a mean of 70 and deviation of 5 put most students between 65 and 75.
Questions people ask
Sample or population — which should I pick?
Population when your numbers are the entire group you care about, such as every employee in one office. Sample when they are a subset used to estimate a wider group. The sample formula divides by n−1, which makes the result slightly larger and corrects a known bias.
What does the standard error tell me?
It estimates how much the mean itself would wobble if you drew another sample of the same size. It shrinks as the sample grows, which is why bigger samples give averages you can lean on more heavily.
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Updated: 2026-08-07