Percentage Difference Calculator Between Two Numbers
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Percentage Difference Calculator
The percentage difference compares two numbers of equal standing — two prices, two measurements, two offers — and expresses their gap as a percentage of their average. Because neither number is treated as the starting point, the answer is the same whichever order you enter them in.
The percentage difference formula
Percentage difference = |a − b| ÷ ((a + b) ÷ 2) × 100
Example: one shop sells a keyboard for 40 and another for 60. The absolute difference is 20 and the average price is 50, so the percentage difference is 20 ÷ 50 × 100 = 40%.
Difference vs. change — don't mix them up
If one of your numbers is a "before" and the other an "after", you want percentage change, which divides by the starting value and carries a sign. Percentage difference divides by the average and is always positive. Comparing 40 → 60 as a change gives +50%; as a difference it gives 40%. Both are correct — for different questions.
Where it's used
Comparing quotes from two suppliers, benchmarking two lab measurements, checking how far apart two salaries or rents are, or quantifying the gap between two survey results. For everyday "what is X% of Y" math, head to the percentage calculator.
FAQs
Take the absolute difference between the two numbers and divide it by their average, then multiply by 100. For 40 and 60: |40 − 60| = 20, the average is 50, so the difference is 20 ÷ 50 × 100 = 40%.
Percentage difference = |a − b| ÷ ((a + b) ÷ 2) × 100. The result is always positive because the comparison has no direction.
Because neither number is the reference point. Dividing by the average treats both values equally, so comparing 40 to 60 gives the same result as comparing 60 to 40 — which is not true for percentage change.
Use percentage difference to compare two things of equal standing — two prices from different shops, two measurements, two salaries. Use percentage change when one value is 'before' and the other is 'after'.
Yes. Comparing 10 and 90: the difference is 80 and the average is 50, so the percentage difference is 160%. The maximum possible value is 200%, approached when one value is near zero.