Percentage Calculator
Most people who search for a percentage calculator actually need one of three different answers: what a percentage of a number is, what percentage one number is of another, or how much something changed in percentage terms. This tool covers all three — just pick the calculation you need from the dropdown below.
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How It Works
All three modes use the same core idea: a percentage is just a fraction of 100.
- X% of Y = (X ÷ 100) × Y
- X is what % of Y = (X ÷ Y) × 100
- Percentage change = ((New − Old) ÷ Old) × 100
The last formula is the one people most often get wrong, because the result is always relative to the original number, not the new one. Going from 50 to 75 is a 50% increase, but going from 75 back down to 50 is a 33.3% decrease — not 50% — because the base value changed.
Worked Example
A few common cases side by side: 20% of 150 is 30. If you scored 45 out of 60 on a test, that's 75% (45 is 75% of 60). And if a subscription price rose from $8 to $10, that's a 25% increase — but if it later dropped back from $10 to $8, that's only a 20% decrease, not 25%, because percentage change is always measured against the starting value, and the starting value is different each direction.