Percentage Difference Calculator
Percentage difference compares two values symmetrically, using their average as the reference. Use it when neither value is clearly the “original” — for example comparing two prices or two measurements.
Worked example
100 vs 120: (20 ÷ 110) × 100 ≈ 18.18%
How to calculate
- Enter the first value.
- Enter the second value.
- Read the relative difference — the result is the same whichever value you enter first.
Formula
Difference = (|A − B| ÷ ((A + B) ÷ 2)) × 100
Explanation
- Comparing two quotes, suppliers or measurements.
- Science and engineering: comparing two experimental readings.
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Use CalculatorFrequently Asked Questions
Difference vs change — which one do I need?
Use percentage change when one value is the reference (before → after). Use percentage difference when comparing two values with no natural reference.
Why divide by the average?
Dividing by the average makes the result symmetric: swapping the two values gives the same percentage, which is what “difference” should mean.