Percentage Difference
Compares two values with no "before/after" direction — useful when neither number is the original.
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How to calculate the percentage difference
- Type the first value in Value A.
- Type the second value in Value B.
- Read the percentage difference, which is the same whichever way round you enter them.
Difference vs. change — what's the distinction?
Percentage change assumes one number is the "before" and one is the "after" — direction matters. Percentage difference treats both numbers as equals with no direction, useful when comparing two independent measurements rather than tracking one value over time.
% difference = (|A − B| ÷ ((A + B) ÷ 2)) × 100
Questions about percentage difference
How is percentage difference calculated?
Take the gap between the two values, divide it by their average and multiply by 100. For 40 and 60: 20 ÷ 50 × 100 = 40%.
When should I use percentage difference instead of percentage change?
Use percentage difference when neither number is the starting point, such as comparing two shops’ prices or two measurements. Use percentage change when one value came first.
Why is the percentage difference of 40 and 60 not 50%?
50% is the change from 40 up to 60, measured against 40. Percentage difference measures against the average (50), so it gives 40%, the same in both directions.
Can the percentage difference be negative?
No. It uses the size of the gap, so it is always zero or positive.