Coefficient of Variation Calculator
Find relative variability as a percentage of the mean.
Results update as you type.
How it works
The coefficient of variation, or CV, measures how much a data set varies relative to its mean, and this calculator computes it from the mean and standard deviation. You enter both, and it returns the CV as a percentage. While the standard deviation tells you the absolute spread of data in its original units, it cannot fairly compare variability between data sets measured in different units or with very different averages. The CV solves this by dividing the standard deviation by the mean, producing a dimensionless ratio, usually shown as a percentage, that captures relative variability. For example, a standard deviation of ten is large relative to a mean of twenty but small relative to a mean of a thousand; the CV makes this immediately clear. It is widely used in finance to compare the risk of investments per unit of return, in laboratory science to judge measurement precision, in quality control, and in comparing the consistency of processes. A lower CV indicates more consistent, less variable data relative to its size. Because the CV divides by the mean, it is most meaningful for data measured on a ratio scale with a true zero and a positive mean. Enter the mean and standard deviation to compute the coefficient of variation.
CV = (standard deviation / mean) × 100
The coefficient of variation expresses the standard deviation as a percentage of the mean, dividing the two and multiplying by 100. Because it is a ratio, it is dimensionless and lets you compare the relative variability of data sets that have different units or very different averages, which the standard deviation alone cannot do. A higher percentage means more variability relative to the average.
Source:Descriptive statistics
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Worked example
How to use this calculator
- 1
Enter your values
Enter mean and standard deviation.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
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Frequently asked questions
What is the coefficient of variation?
The coefficient of variation is a measure of relative variability, defined as the standard deviation divided by the mean, expressed as a percentage. It shows how large the spread of a data set is compared with its average. Because it is dimensionless, it allows fair comparison of variability between data sets with different units or scales.
Why use CV instead of standard deviation?
Standard deviation measures spread in absolute terms, so it cannot compare variability across data sets with different means or units. A standard deviation of five means different things for data averaging ten versus data averaging a thousand. The coefficient of variation normalises by the mean, giving a relative measure that makes such comparisons meaningful and fair.
What is a good coefficient of variation?
It depends entirely on the context. In laboratory measurements a CV below a few percent may indicate good precision, while in finance or biology much higher values are normal. There is no universal threshold; the CV is most useful for comparing the relative variability of similar quantities rather than judging a single value against a fixed standard.
When should I not use the CV?
The CV is unreliable when the mean is close to zero, because dividing by a tiny mean produces an enormous or unstable value, and it is meaningless for data that can be negative or that lack a true zero, such as temperatures in Celsius. It is best applied to positive, ratio-scale data where a mean of zero is impossible.
How is CV used in finance?
In investing, the coefficient of variation measures risk per unit of return by dividing the standard deviation of returns by the expected return. It lets you compare investments with different average returns on an equal footing: a lower CV means less volatility for each unit of expected return, which many investors prefer when weighing risk against reward.