Percentage Difference Calculator
Compare two values of equal standing using the difference relative to their average.
What the Percentage Difference Calculator does
Percentage difference is used when neither value is the reference — comparing two lab measurements, two suppliers, or two readings of the same quantity. Because it divides by the average, the answer is the same whichever order you enter the values.
Formula
Percentage difference = (|A − B| ÷ ((|A| + |B|) ÷ 2)) × 100
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| First value | number | Yes | — |
| Second value | number | Yes | — |
How to use it
- Enter First value and Second value.
- Select Calculate.
Worked example
Two scales report a sample as 48 g and 52 g.
- First value
- 48
- Second value
- 52
|48 − 52| ÷ 50 × 100 = 8% difference.
Reading the result
- Percentage difference divides by the average of the two values, so the answer is the same whichever order you enter them.
- Use it when neither value is the reference — two lab readings, two suppliers. Use percentage change when one value is a clear starting point.
Common mistakes
- Using percentage difference where percentage change is meant, which gives a smaller number because the denominator is larger.
- Comparing values with opposite signs, where the average can approach zero and the percentage becomes meaningless.
Frequently asked questions
When should I use difference instead of change?
Use difference when the two values are interchangeable. Use change when one clearly came first.