Percentage Difference Calculator
Compare two values when neither one is the "original" — the difference is measured against their average.
The formula
Percentage difference = |A − B| ÷ ((A + B) ÷ 2) × 100. Because the base is the average, the result is the same whichever order you enter the values — that is exactly what makes it the right choice for comparisons: two measurements of the same thing, two quotes for the same job, two test scores. When one value is genuinely the starting point, percentage change is the honest measure instead.
Worked examples
Two scales read 48 kg and 52 kg for the same object: |48 − 52| ÷ 50 × 100 = 8% difference. Two values that are equal have a difference of 0%. A value and double that value (say 50 and 100) differ by 50 ÷ 75 × 100 = 66.67% — not 100%, because the base is the average, 75.