Measure spread relative to the mean. Paste your numbers to get the coefficient of variation (CV, also called relative standard deviation) as a percentage, along with the mean and standard deviation, worked steps, and an optional side-by-side comparison with a second dataset.
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How to use the Coefficient of Variation Calculator
Paste or type your data, separated by commas, spaces or new lines.
Choose sample or population: sample if your data is a subset of a larger group.
Optionally add a second dataset to compare which one varies more relative to its mean.
Read the CV with the mean and standard deviation it is based on.
Check the deviations table or copy the results.
Coefficient of variation formula
CV = (s ÷ x̄) × 100% for a sample, or CV = (σ ÷ μ) × 100% for a population, where
x̄ = Σx ÷ n is the mean,
s = √(Σ(x − x̄)² ÷ (n − 1)) is the sample standard deviation and σ = √(Σ(x − μ)² ÷ N) the population one.
Example: fill weights 48.2, 51.5, 49.8, 50.4, 47.9, 52.1, 50.0 and 49.3 g have a mean of 49.9 g and a sample SD of 1.46 g, so CV = 1.46 ÷ 49.9 = 2.93%.
Comparing variability with the CV
Dataset
Mean
SD
CV
Stock A price ($)
103.13
4.55
4.41%
Stock B price ($)
21.46
3.09
14.41%
Stock A has the larger standard deviation in dollars, but relative to its price Stock B swings more than three times as much. That is exactly the comparison the CV is designed for.
CV
Rough interpretation
< 10%
Low variability
10–20%
Moderate
20–30%
High
> 30%
Very high
Frequently asked questions
What is the coefficient of variation?
The coefficient of variation (CV) is the standard deviation divided by the mean, usually shown as a percentage: CV = (s ÷ x̄) × 100%. It expresses the spread of the data relative to its average, so it has no units.
When should I use the CV instead of the standard deviation?
Use the CV to compare variability between datasets with different units or very different means, for example the price volatility of a $20 stock and a $100 stock, or the precision of two lab methods measuring at different concentrations.
Should I use the sample or population formula?
Use the sample formula (dividing by n − 1) when your data is a sample from a larger population, which is the usual case. Use the population formula (dividing by N) only when you have every member of the group.
What is a good coefficient of variation?
It depends on the field. As a loose rule of thumb, under 10% is low variability, 10–20% moderate and above 30% high. Analytical lab methods often aim for a CV below 5%, while biological or financial data can have much higher CVs.
Is the CV the same as relative standard deviation (RSD)?
Yes. Relative standard deviation, %RSD and percent CV are the same quantity: standard deviation divided by the mean, times 100.
Why can't I use the CV with negative numbers or temperatures in °C?
The CV assumes a true zero (a ratio scale). If the mean is near 0 the CV explodes, and on interval scales like °C or °F the CV changes when you change units, so it has no fixed meaning. Use it for positive measurements such as length, weight, time or money.
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