Standard Deviation Calculator

Calculate the standard deviation and variance for sample or population data sets.

What Is a Standard Deviation Calculator?

Calculate standard deviation, variance, z-scores, and confidence intervals for any data set.

Get a comprehensive statistical analysis with population and sample options.

How to Calculate Standard Deviation

Follow these steps:

  • Enter your numbers separated by commas, spaces, or new lines.
  • Choose population or sample standard deviation.
  • Click calculate to see all statistics.

Tips

  • Use population standard deviation when you have all data points.
  • Use sample standard deviation for subsets of data.
  • Z-scores help identify outliers.

Frequently Asked Questions

What is standard deviation?+
Standard deviation measures how spread out data is from the mean. A low standard deviation means data points cluster close to the mean. A high standard deviation means they are widely spread. It is expressed in the same units as the data.
Population vs sample standard deviation?+
Population standard deviation (σ) divides by N — used when you have all data points. Sample standard deviation (s) divides by N-1 — used when you have a sample from a larger population. The N-1 correction (Bessel's correction) makes the sample standard deviation an unbiased estimator.
What is a z-score?+
A z-score tells you how many standard deviations a value is from the mean. Z=0 is at the mean. Z=1 is 1 standard deviation above. Z=-2 is 2 below. About 68% of data falls within ±1 standard deviation and 95% within ±2.

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Standard Deviation Calculator — free online standard deviation calculator, variance calculator, z score calculator, statistics calculator, confidence interval calculator. No signup required. Works in your browser.