What is the difference between percentage difference and percentage change?

Percentage change uses the old value as its base and has a direction. Percentage difference uses the average of both values and has no direction.

How do I calculate percentage difference?

Take the absolute gap between the numbers, divide by their average and multiply by 100.

Can the percentage difference exceed 100%?

Yes, when the values differ a lot. Between 10 and 100 the difference is about 163.6%.

Why does it give a different answer from percentage increase?

The base is different. Percentage increase divides by the starting value, while percentage difference divides by the average of the two.

Percentage Difference Calculator

Compare two numbers as a percentage when neither one is the starting point.

Updated September 19, 2026Checked by the editorial team

First value

Second value

Percentage difference

22.2222%

|80 − 100| ÷ ((80 + 100) ÷ 2) × 100 = 20 ÷ 90 × 100

Percentage difference compares two values that are peers, such as two quotes, two measurements or two schools, where neither one is the original. It uses the average of the two numbers as the base, so the answer is the same whichever way round you enter them.

If one number really is the starting point, use the percentage increase or decrease calculator instead.

How percentage difference calculator works

Enter the two values. The tool finds the gap between them, divides it by their average and shows the result as a percentage.

Because the base is symmetric, swapping the two inputs never changes the answer. That is the main difference from percentage change.

The formula

% difference  =  |A − B| ÷ ((A + B) ÷ 2) × 100

The vertical bars mean absolute value, so the result is never negative.

Worked example: two quotes, 40 and 60

Gap: |40 − 60| = 20.

Average: (40 + 60) ÷ 2 = 50.

20 ÷ 50 = 0.40, so the percentage difference is 40%.

By contrast, going from 40 to 60 is a 50% increase, and going from 60 to 40 is a 33.3% decrease.

When to use this tool

Comparing two supplier quotes or two product prices.
Checking how far a measured value is from a second measurement in a lab or a workshop.
Comparing two groups, such as class averages or regional figures, without picking one as the baseline.

Common mistakes to avoid

Using this formula when one value is a clear before or after. Percentage change is the right tool there.
Reading the answer as a percentage of either number. It is a percentage of their average.
Reporting 40% difference and 50% increase for the same pair without saying which is which.

Frequently asked questions

What is the difference between percentage difference and percentage change?: Percentage change uses the old value as its base and has a direction. Percentage difference uses the average of both values and has no direction.
How do I calculate percentage difference?: Take the absolute gap between the numbers, divide by their average and multiply by 100.
Can the percentage difference exceed 100%?: Yes, when the values differ a lot. Between 10 and 100 the difference is about 163.6%.
Why does it give a different answer from percentage increase?: The base is different. Percentage increase divides by the starting value, while percentage difference divides by the average of the two.

Learn more

Results are for information only and are not financial, legal or medical advice. The calculation logic is covered by automated tests, and examples on this page are worked out and re-checked before publishing. Spotted a mistake? Tell us.