Coefficient of Variation Calculator
Find the coefficient of variation, the standard deviation as a percentage of the mean, from a data set or from a known mean and standard deviation.
Coefficient of variation formula
CV = standard deviation ÷ mean × 100%
Because CV is relative to the mean, it lets you compare the spread of data sets with different units or very different averages.
Worked example
For 10, 12, 14, 16, 18 the mean is 14 and the sample standard deviation is √10 ≈ 3.162. CV = 3.162 ÷ 14 × 100 = 22.59%. Using the population standard deviation (2.828) gives 20.20%.
When to use CV
- Comparing consistency between measurements on different scales.
- Checking the precision of lab assays, where a low CV means repeatable results.
- Comparing risk relative to return in finance.
CV is only meaningful for data measured on a ratio scale with a true zero, and it becomes unstable when the mean is close to zero.
Frequently asked questions
What is a good coefficient of variation?
It depends on the field. In many lab settings a CV under 10% is considered good precision.
Should I use sample or population SD?
Use sample SD when your data are a sample from a larger group, which is the usual case.
Can CV be over 100%?
Yes, when the standard deviation is larger than the mean.
Does CV have units?
No. It is a ratio, usually written as a percentage.
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