A standard deviation calculator computes the spread of a dataset around its mean.
About this calculator
A standard deviation calculator computes the spread of a dataset around its mean. A low standard deviation means values are clustered close to the mean; a high standard deviation indicates values are spread widely.
Standard deviation is used in statistics, quality control, finance (measuring investment volatility), and science. The calculator provides both population standard deviation (for complete datasets) and sample standard deviation (for a sample from a larger population).
Common uses
- Measure the variability of test scores in a class
- Calculate investment return volatility for portfolio analysis
- Assess manufacturing consistency through process standard deviation
- Identify outliers more than 2–3 standard deviations from the mean
Frequently asked questions
What is the difference between population and sample standard deviation?
Population SD divides by N (total observations) and is used when you have data for the entire population. Sample SD divides by N−1 (Bessel's correction) and is used when your data is a sample from a larger population. Sample SD is slightly larger, which corrects for underestimation when working with samples.