Practical tools for measured work
Standard deviation calculator
Calculate sample or population standard deviation, variance, mean and median.
Calculate the layout, check the diagram, then print the result for the shop or jobsite.
Separate numbers with spaces, commas or semicolons; use a decimal point.
How it works
Variance is the sum of squared deviations from the mean divided by n for a population or n−1 for a sample. Standard deviation is the square root of variance. The example dataset has mean 5, population variance 4 and population standard deviation 2.
Current-input example
The result above uses these exact values. This snapshot is included when the page is printed so the output can be checked against the original measurements.
- Data values
- 2 4 4 4 5 5 7 9
- Statistical convention
- Population (divide by n)
Primary result: Standard deviation: 2.
Before using the result
- Check the selected mode, units and input values before using the result.
- Read the assumptions and rounding rules; compare the worked example with your intended calculation.
- A numerical result does not supply missing context or change the stated limitations.
Limitations
Enter up to 10,000 finite numbers with magnitude at most 10^100. Sample deviation needs at least two values. Values are unweighted; missing entries, decimal commas and thousands separators are not inferred.
Frequently asked questions
Are the displayed decimals exact?
Fractions, combinations and integer multiples use exact integer arithmetic. Other results use floating-point arithmetic and are rounded for display. Keep the exact fraction when a repeating decimal matters.
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