Standard Deviation Calculator
When you need to solve standard Deviation, the Standard Deviation Calculator gives you a clear result to review. Try a known example if you are checking your work.
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Last reviewed January 15, 2026 — see our editorial & accuracy policy.
Method: Population σ = √(Σ(x−μ)²/N); sample s uses N−1 (Bessel's correction). Both are shown so you can pick the one matching your data.
How it works
Standard deviation measures how spread out numbers are around the mean. First find the mean, then the average of the squared differences from the mean (the variance), then take its square root. The sample version divides by n − 1, while the population version divides by n.
How to use the Standard Deviation Calculator
Enter the values requested by the tool and start with one realistic example. Read the result together with its unit or label, then change one input at a time if you want to compare options. Keeping a note of the original figures makes the calculation easier to check later.
A result is only as useful as the values and settings entered. Try a simple known example if you want to check your working.