Standard Deviation Calculator
Calculate sample or population standard deviation and variance from your data set, free and instant with no signup in your browser.
Data
Runs in your browser. Your data is not uploaded or stored.
Result
Paste some numbers to see the statistics.
How to use this calculator
- Paste your numbers (commas, spaces or new lines).
- Read both the sample and population standard deviation, plus variance and a summary.
How it works
Standard deviation measures spread around the mean. Sample divides by n−1 (Bessel's correction); population divides by n.
Worked example
2,4,4,4,5,5,7,9. Population σ = 2; sample s ≈ 2.14.
Common mistakes
- Using population standard deviation when you have a sample (use n − 1).
- Forgetting to square the differences from the mean.
Tips
- Runs entirely in your browser. Your inputs are not saved or transmitted.
Frequently asked questions
Sample or population standard deviation?
Use sample (÷ n − 1) when your data is a sample of a larger group; use population (÷ n) only when you have every member.
What does standard deviation tell me?
How spread out the values are around the mean — a low value means the data clusters near the mean.
Sample or population?
Use sample when your data is a sample of a larger group; population when it's the entire set.
Privacy?
Runs entirely in your browser. Your inputs are not saved or transmitted.
Related tools
- Median Calculator
- Mode Calculator
- Percentile Calculator
- Z-Score Calculator
- Binomial Probability Calculator
- Confidence Interval Calculator
Explore more in Maths, Education & Science.
Cite this tool
Zerdly. (2026). Standard Deviation Calculator. Retrieved from https://www.zerdly.com/tools/standard-deviation-calculator/
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.