Coefficient of Variation (Relative Spread)

Excel Formulas › Statistics

All versionsSTDEV

Which dataset is more consistent? Standard deviation alone can’t say — a big mean inflates it. The coefficient of variation (CV) divides the spread by the mean, giving a unit-free percentage you can compare across very different scales.

Quick formula: for values in B2:B20:
=STDEV(B2:B20) / AVERAGE(B2:B20)
Format as a percentage. A CV of 15% means the standard deviation is 15% of the mean — lower is steadier.

Functions used (tap for the full reference guide):

STDEVAVERAGE

The example

Two products’ monthly sales — same average, different consistency.

ABC
1MeasureProduct AProduct B
2Average100100
3Std dev1234
4CV12%34%

The formula

Relative spread as a percentage:

=STDEV(B2:B20) / AVERAGE(B2:B20) // Product A 12% vs B 34% → A is steadier

How it works

CV normalizes the spread so scales don’t matter:

  1. Compute the standard deviation with STDEV (sample) — the absolute spread of the data.
  2. Divide by the mean from AVERAGE. This strips out the units and the scale.
  3. The result is a ratio; format it as a percentage. 12% means the typical deviation is 12% of the average.
  4. Because it’s unit-free, you can compare a CV across datasets with totally different magnitudes — sales in dollars vs counts in units.

Sample vs population: use STDEV (or STDEV.S) when your data is a sample, and STDEVP (STDEV.P) when it’s the entire population. The CV formula is the same — just swap the standard-deviation function.

Try it: interactive demo

Live demo

Enter values (one per line); see the CV.

Mean:   StDev:   CV:

Variations

Population CV

Whole population, not a sample:

=STDEVP(B2:B20) / AVERAGE(B2:B20)

As a clean percentage

Round for reporting:

=ROUND(STDEV(B2:B20)/AVERAGE(B2:B20), 3)

Inverse (consistency ratio)

Higher = steadier:

=AVERAGE(B2:B20) / STDEV(B2:B20)

Pitfalls & errors

Mean near zero breaks it. Dividing by a tiny or zero average produces a huge or #DIV/0! result. CV is only meaningful for data with a positive, non-trivial mean.

Not for data with negatives. CV assumes positive values (like the ratio scale of sales or measurements). Mixed-sign data makes it meaningless.

Sample vs population. STDEV and STDEVP differ; small samples especially. Pick the one that matches your data.

Practice workbook

📊
Download the free Coefficient of Variation (Relative Spread) practice workbook
A CV comparison sheet with sample/population and consistency-ratio variants, plus 4 challenges with answers. No sign-up required.

Frequently asked questions

How do I calculate the coefficient of variation in Excel?
Divide the standard deviation by the mean: =STDEV(B2:B20)/AVERAGE(B2:B20), then format as a percentage. It measures spread relative to the average.
When should I use CV instead of standard deviation?
When comparing variability across datasets with different scales or units. CV is unit-free, so a 12% CV is comparable whether the values are dollars or counts.
Should I use STDEV or STDEVP?
Use STDEV (sample) when your data is a sample of a larger group, and STDEVP (population) when it represents the entire population.

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Related formulas: Standard deviation · Percentile & quartile · Z-score (standardize)

Function references: STDEV · AVERAGE