Percentage Difference Calculator
Type two values to see how far apart they are as a percentage of their average, the fair comparison when neither one is the original.
What’s the % difference between and ?
Percentage difference
8%
48 and 52 differ by 8% of their average size, 50.
The line marks their average, 50: the gap is measured against it.
How this works: Method, 1 source, Checked against 1 worked example,
How this works
Method
Use percentage difference when two values are on an equal footing, such as two shops’ prices or two lab measurements, and neither is the “before”. Take the absolute gap between them and divide it by their average, then multiply by 100. For 48 and 52 the gap is 4, the average is 50, and 4 ÷ 50 = 8%. Full method
Sources
How it’s tested
One worked example for this page is checked by automated tests before every release: given the inputs, the tool must show the expected answer.
Privacy
On your device. Nothing you enter or open leaves this browser. Without AI, everything stays on this device. If you added your own AI key, Ask sends your question (or, for Explain my result, the figures) to that provider. Built-in browser AI keeps it here. Until you add your own AI key, nothing can be sent. About privacy labels
Changes
- Added eight pages for common questions, from percent of a number to percent error and reverse percentages, each with its own method, examples and table.
- Added key facts with a worked example of each formula.
- Redesigned: type the numbers straight into a sentence, with bars on one scale that picture the answer.
- Results now update as you type, with no Calculate button.
- First published.
How to calculate percentage difference
Use percentage difference when two values are on an equal footing, such as two shops’ prices or two lab measurements, and neither is the “before”. Take the absolute gap between them and divide it by their average, then multiply by 100. For 48 and 52 the gap is 4, the average is 50, and 4 ÷ 50 = 8%.
Because the average treats both values alike, the answer does not depend on the order: 48 vs 52 and 52 vs 48 both give 8%. Percentage change would give two different answers here, +8.33% going up and −7.69% going down.
For values of opposite sign, the average is taken of their sizes (|a| + |b|) ÷ 2, so 5 and −5 differ by 200% instead of dividing by zero. The largest possible percentage difference is 200%, reached when one value is zero or the signs are opposite.
% difference = |a − b| ÷ ((|a| + |b|) ÷ 2) × 100
- Using the mean of the two values as the reference value is one of the standard choices for a relative difference when neither value is the reference. Source: Wikipedia, Relative change.
Percentage difference compared with percentage change
The difference is the same both ways round; the change depends on which value you start from.
| Values | % difference | % change a → b | % change b → a |
|---|---|---|---|
| 48 and 52 | 8% | 8.33% | −7.69% |
| 10 and 12 | 18.18% | 20% | −16.67% |
| 90 and 110 | 20% | 22.22% | −18.18% |
| 100 and 150 | 40% | 50% | −33.33% |
| 1 and 2 | 66.67% | 100% | −50% |
| 3.2 and 3.5 | 8.96% | 9.38% | −8.57% |
| 250 and 400 | 46.15% | 60% | −37.5% |
| 0.8 and 1 | 22.22% | 25% | −20% |
| 60 and 40 | 40% | −33.33% | 50% |
| 75 and 80 | 6.45% | 6.67% | −6.25% |
Show all 12 rowsShow fewer
| 5 and 15 | 100% | 200% | −66.67% |
| 1000 and 1001 | 0.1% | 0.1% | −0.1% |
Frequently Asked Questions
When should I use percentage difference instead of percentage change?
Use change when there is a clear before and after (a price last year and this year). Use difference to compare two things side by side, like the same item in two stores.
What is the percentage difference between 10 and 20?
The gap is 10 and the average is 15, so it is 10 ÷ 15 = 66.67%. As a change, 10 to 20 is +100% and 20 to 10 is −50%.
Can the percentage difference be more than 100%?
Yes, up to 200%. 1 and 5 differ by 4 ÷ 3 = 133.33%, and 0 and any other number differ by 200%.