Standard Deviation Calculator
Sample and population standard deviation, variance, mean and a z-score table for any list of numbers.
Result
How to use
- 1
Paste or type your numbers — commas, spaces or one per line all work.
- 2
Choose sample (most class or survey data) or population (every member is included).
- 3
See the standard deviation, variance and the z-score of every value.
Questions
What is the difference between sample and population standard deviation?
Population SD divides the sum of squared deviations by N. Sample SD divides by N − 1 (Bessel's correction) because a sample tends to underestimate the spread. Use sample SD when your numbers are only part of a larger group.
What does a z-score tell me?
How many standard deviations a value is from the mean: z = (x − mean) ÷ SD. A z-score of +2 means the value is two SDs above average; about 95% of normally distributed values lie between −2 and +2.
What is the coefficient of variation?
SD ÷ mean × 100. It compares spread between data sets with different averages — for example the consistency of two batsmen's scores.
About this Std Deviation tool
Standard Deviation Calculator — Sample and population standard deviation, variance, mean and a z-score table for any list of numbers. It is one of 200 free tools on namasivayam.in, made by software engineer Namasivayam Vadivelan for everyday use in India.
Everything is calculated instantly in your browser: nothing you type or upload is sent to any server, there is no sign-up, and it works on mobile and desktop. Paste or type your numbers — commas, spaces or one per line all work.
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Results are estimates to help you plan. They are not financial, tax or medical advice.