Standard Deviation Calculator

Use the sample formula (divide by N − 1) when your numbers are a sample drawn from a larger population — this is the default and what most statistics courses teach. Use the population formula (divide by N) only when your numbers represent the entire population. Switch with the toggle above the inputs.

The calculator splits the input on commas and whitespace, parses each token with Number(), and drops anything that does not produce a finite number — including Infinity and NaN. It does not show an error; it just ignores those tokens.

Sample standard deviation divides by N − 1, which is zero when N = 1, and dividing by zero is undefined. The calculator returns 0 in that case rather than NaN, but the value is not statistically meaningful — you need at least two observations.