Percentage Change Calculator
Percentage change and percentage difference between two values, chained changes that compound (+10 % then −5 %), and the original value before a change.
Change relative to the start and the symmetric difference, the compounded result of several changes with the single equivalent rate, and what it takes to undo a change.
Example: 80 → 100 is +25 % (difference 22.2 %); +10 %, −5 %, +20 % on 200 compound to 1.254 = +25.4 %, not +25 %; a +25 % rise is undone by −20 %, not −25 %.
Percent of what?
Always of the start.
The three questions the page answers and the two mistakes it points out.
Change vs difference
Percentage change is (B − A) / |A| × 100: it depends on which value is the start, so 80 → 100 is +25 % but 100 → 80 is −20 %. Percentage difference is symmetric — |A − B| divided by their mean — and is used when neither is the starting point.
Chained changes compound
Successive changes multiply rather than add: +10 % then −5 % then +20 % is 1.10 × 0.95 × 1.20 = 1.254, an overall +25.4 %, not +25 %. The page shows every step and the single per-step rate that would give the same result (the geometric average).
Undoing a change
A value that rose 25 % must fall 20 % to return, because the fall is taken from the larger base: the reversing change is 1/(1 + p/100) − 1. The original value before a known change is B / (1 + p/100); a change of −100 % leaves nothing to reverse. Nothing leaves the browser; the same four anonymous usage counts as the rest of the site apply.
SOURCES
- Percentage change (B − A)/|A|, symmetric percentage difference |A − B| / mean(A, B), multiplicative compounding of successive changes (arithmetic definitions)
Last reviewed 20 September 2026. How results are checked: How we verify.