Percentage Difference Calculator
Find the percentage difference between two values, relative to their average.
Enter two values to find the percentage difference between them. Unlike percentage change, percentage difference is symmetric — it doesn't matter which number you put first — because it is measured against the average of the two.
Use it when neither value is a clear “before” or “after”, such as comparing two measurements or two prices.
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Formula
Percentage difference
(|a − b| ÷ ((a + b) ÷ 2)) × 100 = difference %
The absolute difference divided by the average of the two values. Example: 40 and 60 → 20 ÷ 50 × 100 = 40%.
How to use the percentage difference calculator
- 1Enter the first value.
- 2Enter the second value.
- 3Read the percentage difference; copy or share it.
Examples
| Example | Input | Result |
|---|---|---|
| Two values | 40 and 60 | 40% |
| Order doesn't matter | 60 and 40 | 40% |
| Close values | 100 and 110 | 9.52% |
Percentage difference vs. percentage change
Percentage change measures movement from a starting value to an ending value, so it has a direction (increase or decrease) and depends on which value is the base. Percentage difference compares two values without treating either as the reference: it divides the absolute difference by their average, so swapping the two numbers gives the same answer.
Use percentage change for before-and-after situations (last month vs. this month). Use percentage difference for symmetric comparisons (measurement A vs. measurement B), where there is no natural starting point.
Worked example
For 40 and 60: the absolute difference is 20, the average is 50, so the percentage difference is 20 ÷ 50 × 100 = 40%. Note this differs from percentage change — going from 40 to 60 is a 50% increase, while going from 60 to 40 is a 33.3% decrease, yet the percentage difference between them is 40% either way.
Frequently asked questions
How do I calculate percentage difference?
Take the absolute difference between the two values, divide by their average, and multiply by 100. For 40 and 60: 20 ÷ 50 × 100 = 40%.
How is it different from percentage change?
Percentage difference is symmetric and uses the average as the base; percentage change has a direction and uses the starting value as the base.
When should I use percentage difference?
When comparing two values where neither is a clear reference point — for example, two independent measurements or two prices.
Is my data private?
Yes. Calculations happen in your browser only.
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<iframe src="https://numvella.com/embed/percentage-difference-calculator" width="100%" height="460" style="border:1px solid #e2e8f0;border-radius:12px" title="Percentage Difference Calculator — Numvella" loading="lazy"></iframe>Related calculators
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