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Statistics Calculator
Get the mean, median, mode, standard deviation, variance, quartiles and range of a data set in one go.
Standard Deviation Calculator
Calculate the sample or population standard deviation of a data set, with every step shown.
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How to use this calculator
Enter your values. The result updates as you type; press Calculate to confirm and jump to the result on mobile. Use Share to send the calculator with your result.
Formula
Population σ = √( Σ(x − μ)² ÷ N )
Sample s = √( Σ(x − x̄)² ÷ (n − 1) )
Example: 2, 4, 4, 4, 5, 5, 7, 9 has mean 5 and Σ(x − 5)² = 32. Population σ = √(32 ÷ 8) = 2; sample s = √(32 ÷ 7) ≈ 2.138.
Dividing by n − 1 (Bessel’s correction) makes the sample variance an unbiased estimate of the population variance.
Frequently asked questions
What is a “good” standard deviation?
It depends on the data’s scale. Compare it with the mean (coefficient of variation = SD ÷ mean) to judge spread.
About this tool
- Written by
- [Author: to be assigned]
- Reviewed by
- Formula tests passed · human review pending
- Last updated
- 31 Oct 2026
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