Coefficient of Variation Calculator
Measure relative variability as the ratio of standard deviation to mean.
Results update as you type.
About this calculator
The coefficient of variation (CV) expresses the standard deviation as a percentage of the mean, giving a unit-free measure of relative spread. Because it is scale-independent, the CV lets you compare the variability of data sets that have very different means or units — you can put the consistency of a set of body weights next to a set of exam scores even though they share no units.
The formula is simply CV = (standard deviation ÷ mean) × 100%. This calculator uses the sample or population standard deviation you choose, divides it by the mean of the data and flags whether the relative variability is low, moderate or high (below about 15%, between 15% and 30%, or above 30% here).
Worked example: for 10, 12, 14, 16, 18 the mean is 14 and the sample standard deviation is about 3.16, so the coefficient of variation is 3.16 ÷ 14 × 100% ≈ 22.6% — moderate relative variability. The CV is widely used in finance to compare investment risk per unit of return and in the lab to judge the precision of repeated measurements.
Frequently asked questions
What is a high coefficient of variation?
There is no universal cutoff, but a CV below about 15% is often considered low (consistent) variability and above 30% relatively high. Always judge it against typical values for your field.
When is the coefficient of variation not useful?
The CV is unreliable when the mean is near zero, because dividing by a tiny mean makes it explode, and it is not meaningful for data with negative values or data that lacks a true zero point, such as temperatures in Celsius.
How do I calculate the coefficient of variation?
Divide the standard deviation by the mean and multiply by 100 to state it as a percentage. For a mean of 14 and a standard deviation of 3.16, the CV is 3.16 ÷ 14 × 100% ≈ 22.6%.
Why use the CV instead of the standard deviation?
The standard deviation is tied to the units and scale of the data, so you cannot fairly compare the spread of prices in dollars with the spread of heights in centimetres. Dividing by the mean removes the units, letting you compare relative consistency across completely different data sets.
Is the coefficient of variation the same as relative standard deviation?
Yes. Relative standard deviation (RSD) is another name for the coefficient of variation expressed as a percentage; the two terms are interchangeable.
Should I use the sample or population standard deviation?
Use the sample option when your numbers are a subset drawn from a larger group, and the population option when they are the whole group. The choice changes the standard deviation slightly and therefore the CV, especially for small data sets.
API — use this calculator from code
Call this calculator as a free JSON endpoint — no key required. Send the field values below as query parameters or JSON. Read the full API docs →
Endpoint
GET https://calculator.free/api/v1/coefficient-of-variation/curl
curl "https://calculator.free/api/v1/coefficient-of-variation/?numbers=10, 12, 14, 16, 18&type=sample"JavaScript fetch()
const r = await fetch(
"https://calculator.free/api/v1/coefficient-of-variation/?" + new URLSearchParams({
"numbers": "10, 12, 14, 16, 18",
"type": "sample"
}));
const data = await r.json();
console.log(data.results);Results are estimates for general guidance only, not financial, medical or tax advice.