Standard Deviation Calculator
Measure the spread of your numbers. Choose sample or population and see the mean, variance, divisor and steps together. Your data stays in this browser.
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- No sign-up
- Runs in your browser
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Standard deviation
Enter your values and calculate.
Calculation steps
A squared value outside the numeric range is shown as unavailable. The standard deviation is calculated with scaled differences.
Results are approximate floating-point values, shown with up to 12 significant digits. Very large inputs can lose small differences.
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Collect worksheet and lesson links on a VISU Link page. You decide which links to make public; this calculator does not upload your data.
Create a VISU LinkHow to use it
- Paste values and choose the decimal separator. Do not use thousands separators.
- Choose Sample when estimating a larger group, or Population when you have every value in that group.
- Select Calculate to see the standard deviation, mean, variance and steps.
- Copy the result if you want to keep it. Input is not saved automatically.
Examples
A sample with a known result
For 2, 4, 4, 4, 5, 5, 7, 9, the mean is 5. Population variance is 4 and standard deviation is 2. Sample variance is 32/7 and standard deviation is about 2.138089935.
Identical measurements
For 6, 6, 6, all differences are zero, so both sample and population standard deviation are zero.
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Put this tool on your blog, store or club site. It runs inside your page, free, with no account, and a small "by VISU" credit line under it.
Questions
Which standard deviation should I use?
Choose population for the entire group you describe. Choose sample when using these observations to estimate spread in a larger population. The sample formula uses n − 1.
Why does a one-value sample give an error?
The sample divisor is n − 1, which is zero for one value. A complete population of one value has standard deviation zero.
How are large numbers handled?
The calculator uses centred, scaled differences and compensated summation to reduce cancellation and intermediate overflow. Floating-point limits still apply; unsupported values are rejected.
Can I compare independent samples?
Calculate each dataset separately. This tool describes spread; it does not pool samples or run a significance test.
How do I enter decimals and keep the result?
Choose decimal point or comma before calculating. Do not use thousands separators. Copy the calculated summary or download its results CSV; your source values are not saved automatically.