Compare two values with no clear starting point.
Enter two values to see how different they are as a percentage of their average, with the working shown.
Comparing two quotes, two products or two measurements, where neither one came first? A percentage difference calculator gives you one fair figure for how far apart they are. It divides the gap by the average of the two values, so the answer is the same whichever way round you enter them. It also shows the change from A to B and from B to A, in case you need those too.
How to Use the Percentage Difference Calculator
- Enter Value A and Value B. The order does not matter.
- Read the percentage difference, the absolute difference and the average of the two values.
- For comparison, the results also show the change from A to B and from B to A.
The Percentage Difference Formula
Percentage difference = |A − B| ÷ ((A + B) ÷ 2) × 100
- |A − B| is the gap between the two values, ignoring any minus sign.
- (A + B) ÷ 2 is their average.
Percentage Difference Examples
Two quotes of $120 and $150.
Gap: |120 − 150| = 30. Average: (120 + 150) ÷ 2 = 135.
30 ÷ 135 × 100 = 22.22%.
The same pair as a percentage change gives two different answers: 120 to 150 is a 25% increase, but 150 to 120 is a 20% decrease. Percentage difference avoids picking a side.
Two survey results of 45 and 55.
Gap 10, average 50, so 10 ÷ 50 × 100 = 20%.
Percentage Difference vs Percentage Change
| Use | When | Divides by |
|---|---|---|
| Percentage difference | Neither value is the starting point: two shops, two people, two samples | The average of both values |
| Percentage change | One value came first: last year and this year, before and after | The original value |
If you are measuring growth or decline over time, use the percentage change calculator instead.
Percentage Difference vs Percentage Points
When the two values are already percentages, the plain gap between them is measured in percentage points. If 40% of one group and 50% of another said yes, the gap is 10 percentage points. The percentage difference is 10 ÷ 45 × 100 = 22.22%. Say which one you mean when you report it, because the two numbers are easy to confuse.
Where Percentage Difference Is Used
- Comparing prices or quotes from two suppliers.
- Lab work, when comparing two measurements of the same thing and neither is the accepted value.
- Comparing products, such as the battery life of two phones.
- Checking two sets of results, such as two counts of the same stock.
When one value is the correct or accepted value, use the percent error calculator instead.
Mistakes to Avoid
- Dividing by one of the values. That gives a percentage change, which changes depending on the order.
- Leaving the sign in. Percentage difference is always positive, because it measures the size of the gap, not its direction.
- Using it when one value is the “right” answer. Measuring against a known value is percent error.
Questions About Percentage Difference
Can percentage difference be more than 100%?
Yes, when the values are very far apart. For 10 and 100, the gap is 90 and the average is 55, so the difference is about 163.6%. It can never be more than 200%.
Why is percentage difference different from percentage change?
They divide by different numbers. Percentage change divides by the starting value, while percentage difference divides by the average of both. That is why 120 and 150 give 25% as a change, but 22.22% as a difference.
What if one value is negative?
The formula breaks down when the average of the two values is zero or close to it. The calculator tells you if that happens.
For the basics of working with percentages, read how to calculate percentage, or use the percentage calculator for simple percent-of questions.
How we checked this page: each example was worked by hand and matches the calculator, including the change in each direction.