Everyday Tools
Standard Deviation Calculator
Standard deviation and variance, sample and population both shown.
✓ Free
✓ No account
◉ Runs on this device
Everyday Tools
Powering up the tool…
TOOL STANDARD-DEV
What this tool does
About the standard deviation calculator
The n−1 question answered properly, both conventions printed.
How to use it
- Paste the numbers.
- Choose sample or population (sample is the usual).
- Read SD, variance and the other convention alongside.
- Quote which convention you used — it matters at small n.
Useful for
- Quantify spread for a report or assignment.
- Check consistency of timings or measurements.
- Settle the n versus n−1 argument with both shown.
Straight answers
Standard Deviation Calculator FAQ
Sample or population — how do I choose?
Measured everything you care about? Population (÷n). Measured some to infer about more? Sample (÷n−1) — the correction pays for estimating the mean from the same data. Homework defaults to sample; so does this tool.
What does the number MEAN?
Roughly: most values sit within one SD of the mean (about two-thirds, if roughly bell-shaped). SD 2 on a mean of 100 is remarkable consistency; SD 30 is scatter.