How to calculate the coefficient of variation
The coefficient of variation (CV) measures spread relative to the mean. Divide the population standard deviation by the mean and multiply by 100 to get a percent. For 2, 4, 4, 4, 5, 5 the mean is 4 and the population standard deviation is 1, so the CV is 1 ÷ 4 × 100 = 25%. It is a ratio, so you need the spread first from the standard deviation calculator and the mean to divide it by.
How to use this calculator
Enter at least two numbers and leave unused fields blank. The result is a percentage, which lets you compare variability across data sets with different units or scales. For absolute spread, see the standard error calculator.
Why use a relative measure of spread
A standard deviation of 5 means very different things for data centered on 10 versus 1,000. The CV expresses variability as a fraction of the mean, so two distributions can be compared fairly. For the midpoint of the range, see the midrange calculator.
This is why laboratories and manufacturing teams quote CV rather than raw standard deviation when judging whether a method is repeatable — a single percentage threshold can be applied across assays that produce very different magnitudes.
Frequently asked questions
- How do I calculate the coefficient of variation?
- Divide the population standard deviation by the mean and multiply by 100. For 2, 4, 4, 4, 5, 5 the CV is 25%.
- Why is the coefficient of variation a percentage?
- Expressing spread relative to the mean as a percent makes it unitless, so you can compare data sets measured in different units.
- Does this use population or sample standard deviation?
- This calculator divides the sum of squared deviations by n, giving the population standard deviation for the CV.
- When is the CV not useful?
- It is unreliable when the mean is near zero, because dividing by a tiny mean inflates the result.
- Can the coefficient of variation be negative?
- Only if the mean itself is negative, since standard deviation is never negative. For data on a scale that allows negative values, such as temperatures in Celsius or profit and loss, the CV loses its meaning — use standard deviation on its own instead.