Overview
What Is Standard Deviation?
Standard deviation measures how spread out numbers are from their average. A low standard deviation means values cluster close to the mean; a high one means they're spread widely.
Calculate standard deviation and variance instantly.
Standard deviation measures how spread out numbers are from their average. A low standard deviation means values cluster close to the mean; a high one means they're spread widely.
Useful for statistics coursework, quality control, finance, and any data analysis requiring variability measurement.
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Standard deviation and variance update automatically.
Sample standard deviation divides by (n-1) instead of n, correcting for bias when working with a subset of data.
Variance is the average of squared differences from the mean - it's standard deviation squared.
It means your data points are spread widely from the average, indicating more variability.
No, standard deviation is always zero or positive since it's derived from squared differences.
At least two data points are needed for sample standard deviation; population standard deviation can technically use one but isn't meaningful with too few points.
No, they're calculated differently - standard deviation squares differences before averaging, which weights larger deviations more heavily.
Quality control, test score analysis, financial risk assessment, and scientific research all commonly use standard deviation.
Yes, because it squares differences, outliers have an outsized effect on standard deviation.
No, calculations happen entirely in your browser.
Yes, completely free with no sign-up required.