Relative variability — standard deviation as a fraction of the mean
Enter your data to calculate the coefficient of variation (CV) — the standard deviation expressed relative to the mean. The CV is shown as a ratio above; multiply by 100 for a percentage.
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The coefficient of variation (CV) measures relative variability: it is the standard deviation divided by the mean. Because it is a ratio, the CV is unitless, which makes it ideal for comparing the spread of data sets that have different units or very different averages — something the standard deviation alone cannot do.
The CV is CV = s ÷ x̄, the sample standard deviation divided by the mean. It is usually reported as a percentage by multiplying by 100. A CV of 0.25 (25%) means the standard deviation is one quarter of the mean. The measure is most meaningful for data on a ratio scale with a positive mean; it is not appropriate when the mean is zero or can be negative.
Use the CV to compare consistency across groups on different scales — for example, which of two assets is more volatile relative to its average return, or which measurement method is more precise. A lower CV indicates less relative variability. Because it divides by the mean, the CV becomes unstable when the mean is close to zero.
Divide the standard deviation by the mean: CV = s / mean. Multiply by 100 to express it as a percentage.
It is commonly reported as a percentage (CV × 100), but the underlying value is a unitless ratio. This calculator shows the ratio; multiply by 100 for the percentage form.
When the mean is zero or negative, or when the data is not on a ratio scale, the CV can be misleading or undefined.