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Standard Deviation Calculator
Enter your data values below (leave extra boxes blank if you have fewer than 10) to find the mean, variance, and standard deviation.
What standard deviation measures
Standard deviation tells you how spread out a set of numbers is around its average (mean). A small standard deviation means the values are clustered close to the mean; a large one means they’re spread widely.
How this calculator works
Fill in your data values (clear any boxes you don’t need, up to 10 values). The calculator finds the mean, measures how far each value is from that mean, squares those differences, averages them to get the variance, and takes the square root to get the standard deviation.
- Population standard deviation is used when your numbers represent an entire group you care about.
- Sample standard deviation is used when your numbers are a sample drawn from a larger population, and divides by one less than the count (n-1) to correct for that.
This tool is intended for general educational and planning purposes.
Last reviewed August 2026