Is the Standard Deviation Calculator free to use?

Yes. The Standard Deviation Calculator is completely free, runs entirely in your browser, and requires no account or sign-up. Your inputs never leave your device.

Standard Deviation Calculator

Compute standard deviation, variance, and mean for a data set.

Quick answer

Standard deviation measures how spread out numbers are around their mean. It's the square root of the variance — the average of the squared differences from the mean. A small value means data clusters near the average; a large one means it's widely scattered.

Data set

Numbers (comma or space separated)

Data represents

Standard deviation (sample)

1.8708

Variance

3.5

Mean

5.5

Count

Spread around the mean

Standard deviation measures typical distance from the average. In roughly normal data, about 68% of values sit within one SD of the mean and 95% within two — which is why it anchors everything from test scores to quality control.

Sample vs. population

Dividing by n − 1 (Bessel's correction) compensates for the fact that a sample's own mean understates true spread. Use population mode only when your numbers are the entire group of interest, not a sample from it.

Frequently asked questions

How does the Standard Deviation Calculator work?: Standard deviation measures how spread out numbers are around their mean. It's the square root of the variance — the average of the squared differences from the mean. A small value means data clusters near the average; a large one means it's widely scattered.
Is the Standard Deviation Calculator free to use?: Yes. The Standard Deviation Calculator is completely free, runs entirely in your browser, and requires no account or sign-up. Your inputs never leave your device.

Sources & methodology