What is the difference between population and sample SD?
Population SD divides by N, while sample SD uses N−1 to estimate variability from a sample.
Standard Deviation Calculator
Calculate population and sample standard deviation, variance, and mean.
Calculations happen locally. We do not send your values to our server.
Example
For 2, 4, 4, 4, 5, 5, 7, and 9, the population mean is 5 and the population standard deviation is 2.
Calculation method
The tool finds the mean, sums squared distances from that mean, and divides by N for population variance or N−1 for sample variance before taking the square root.
Important notes
Choose the population or sample result according to how the data was collected; a one-value sample deviation is undefined.
Frequently asked questions
Can standard deviation be negative?
No. Squared deviations and their square root always produce a non-negative result.
Does the tool round values before calculating?
No. Full JavaScript numeric precision is used until the results are displayed.