This free online standard deviation calculator measures how spread out a set of numbers is from its mean, reporting both population and sample variance and standard deviation. Enter your data set to see a complete statistical breakdown instantly.
How to Use the Standard Deviation Calculator
Type or paste your list of numbers into the "Enter Numbers" box, separated by commas, spaces, or new lines.
Click "Calculate".
Review the count, mean, population variance/standard deviation, and sample variance/standard deviation in the results table.
Frequently Asked Questions
Population standard deviation divides the sum of squared differences from the mean by n (the count of numbers), assuming your data is the entire population. Sample standard deviation divides by n - 1 instead (Bessel's correction), which is used when your numbers are only a sample drawn from a larger population.
The mean is the sum of all numbers divided by the count. Variance is the average of the squared differences between each number and the mean, and standard deviation is simply the square root of variance.
Sample variance and sample standard deviation require at least two numbers, so with only one value the table shows "N/A — need at least 2 numbers" for those two rows, while population statistics are still shown.
Yes, it's completely free with no sign-up required.