Free tool · Math
Percentage Difference Calculator
See how far apart two values are, as a percentage — without needing to know which came first.
Difference between 80 and 100?
22.22%
The percentage difference between 80 and 100 is 22.22%
How to use this percentage difference calculator
- Enter the first value (A).
- Enter the second value (B) — the order does not matter.
- Read the percentage difference between them. The answer updates as you type.
- Check the step-by-step working under the result to see exactly how the answer was reached.
The percentage difference formula
Percentage difference = (|A − B| ÷ Average of A and B) × 100
The vertical bars mean “absolute value” — drop the sign. The average is (A + B) ÷ 2. Because the formula divides by the average of the two values, neither value is treated as the starting point, and swapping A and B changes nothing.
Worked example — comparing 80 and 100
- Find the absolute difference: |80 − 100| = 20.
- Find the average: (80 + 100) ÷ 2 = 90.
- Divide: 20 ÷ 90 = 0.2222.
- Multiply by 100: 0.2222 × 100 = 22.22%.
Different question, different answer. The same two numbers measured as percentage change give +25% (80 → 100) or −20% (100 → 80), because change picks one value as the base. Difference treats the two as equals — that is the whole point of it. If you have a clear before-and-after, use the Percentage Change Calculator instead.
Examples
| Value A | Value B | Percentage difference |
|---|---|---|
| 80 | 100 | 22.22% |
| 100 | 80 | 22.22% (same — order does not matter) |
| 50 | 60 | 18.18% |
| 200 | 250 | 22.22% |
Frequently asked questions
Is percentage difference the same as percentage change?
No. Percentage difference compares two values as equals, using their average as the base. Percentage change measures movement from an old value to a new one and has a direction. The difference between 80 and 100 is 22.22%; the change from 80 to 100 is +25%.
Does the order of the two values matter?
No. The formula divides by the average of the two values, so swapping them changes nothing: 80 vs 100 and 100 vs 80 both give 22.22%.
When should I use percentage difference instead of percentage change?
When neither number is a “before” — for example, comparing two test scores, two prices for the same product in different shops, or two measurements taken under different conditions. The comparison is peer-to-peer, not before-and-after.
Why does the formula use the average of the two values?
Because the average makes the comparison symmetric. If the formula divided by one of the values instead, the answer would depend on which one you picked, and swapping the order would change the result.
Can percentage difference be negative?
No. The formula uses the absolute difference, so the result is always zero or positive. It measures how far apart two values are, not which one is bigger.
What does a difference of 0% mean?
The two values are identical. A difference of 22.22% means the values are about 22% apart relative to their shared midpoint, their average.