🧮 Percentage Calculator

The four percentage questions people actually type into a search box — “what is X% of Y”, “X is what percent of Y”, “percent change” and “add or subtract a percent” — answered with the arithmetic printed beside the number, so you can check it instead of trusting it. No account, nothing sent anywhere.

Percentages without the usual traps

Percentage points are not percent. A rate moving from 4% to 6% rose by 2 points but by 50%. Politicians and ads switch between the two on purpose — when the base is a percentage itself, always say which one you mean. Percent change has a direction and a base: (new − old) ÷ |old| × 100; the absolute value in the denominator is what keeps a drop from −20 to −10 reading as a 50% gain rather than a nonsense sign flip. A change from zero has no percentage — it is a move from nothing, so the honest answer is “infinite”, not “100%” or “0%”.

Discounts stack multiplicatively, not additively. “30% off, then another 20%” is 0.7 × 0.8 = 0.56 — a 44% saving, not 50%. The same maths explains why a 20% price rise needs only a 16.7% cut to return to the old price, and why “+50% then −50%” leaves you at 75% of where you started.

Part of Everyday Tools. For money maths with a rate and a term, the loan & interest calculator does the compounding properly.