Standard Deviation Calculator
Standard deviation is the square root of variance. It uses the same units as the data.
Standard deviation describes typical distance from the mean. Larger SD means more spread.
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Example problems
How this solver works
- Find the mean.
- Average the squared deviations (divide by n).
- Take the square root.
Formula
Population standard deviation.
Worked examples
simple list
- Mean, then sqrt of variance
Answer: see solver
Common mistakes
Stopping at variance
Variance is in squared units. Standard deviation is the square root.
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Frequently asked questions
Why divide by n − 1?
Sample SD uses n − 1 to correct bias when the mean is estimated from the sample. This tool uses n unless you specify otherwise.