Percentage Calculator
Almost every percentage question in daily life is one of three shapes. This page answers all three at once: what is X% of Y, X is what percent of Y, and the percentage change from A to B.
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Your result appears above and updates as you type.
How it works
Shape one is a multiplication: X% of Y is Y × X/100. Shape two is a division followed by the same hundred: X ÷ Y × 100. Shape three is the one that causes arguments: (new − old) ÷ old × 100. The denominator is the old value — always — which is why a price that falls 50% and then rises 50% does not come back: the rise is calculated on the smaller number, and only returns three quarters of the way.
That asymmetry is also why percentage points and percent are different things. An interest rate moving from 4% to 5% rose by one percentage point and by 25 percent, and both statements are true in different languages.
Good practice & limits
- For tips and discounts, 10% first (move the decimal), then halve it for 5% or double it for 20%.
- When a report says something ‘rose 200%’, it means it tripled. Rose to 200% means it doubled.
- Always ask ‘percent of what?’ — most misleading statistics are honest percentages of a surprising base.