Standard deviation calculator
Paste your numbers. Mean, median, mode, quartiles, variance and standard deviation, all at once.
- Runs in your browser — nothing you enter is uploaded
- No sign-up, no quotas, free to use as often as you like
How it works
Paste the numbers in any shape you have them — a column from a spreadsheet, a comma-separated line, a paragraph with numbers scattered through it. Anything that is not a number is ignored, so you rarely need to tidy the data first.
Sample or population — the distinction that matters
Both are given, because using the wrong one is the classic mistake. Use the sample standard deviation when your numbers are a sample drawn from some larger group and you want to say something about that group; it divides by n−1. Use the population figure only when your numbers are the entire group you care about; it divides by n. For small sets the two differ noticeably, which is exactly when people quote the wrong one.
Mean, median and mode together
All three are shown side by side, because the gap between them is informative. A mean well above the median means a few large values are dragging it up — incomes and house prices do this reliably — and in that case the median describes the typical case better.
Quartiles
The lower and upper quartiles are calculated by linear interpolation, the same method spreadsheets use, so the numbers match what you would get from a QUARTILE function.
What counts as a number
Decimals, negatives and scientific notation are all read. Text, labels and units are skipped, so a pasted spreadsheet column with a header works without editing.
Standard deviation calculator — questions
Which standard deviation should I use?
Sample if your numbers are a sample from a larger group, population if they are the whole group. Both are shown and labelled.
How should I separate the numbers?
However you like — line breaks, commas, tabs or spaces all work, and anything that is not a number is ignored.
What if there is no repeated value?
The mode is reported as having no repeated value rather than picking one arbitrarily.
How are quartiles calculated?
By linear interpolation, matching the method spreadsheets use, so the results agree with a QUARTILE function.
Is my data uploaded?
No. Everything is calculated in your browser.