Percentage Calculator
Three calculators in one — find a percentage of a number, work out what percent one value is of another, or measure the change between two numbers. Results update as you type.
How the percentage calculator works
Pick a mode, type your numbers, and the answer appears instantly — no button to press, no page reload.
X% of Y
Find part of a whole — like a 20% tip on a $150 bill, or 15% off a price. Formula: (X ÷ 100) × Y.
X is what % of Y
Turn a ratio into a percentage — like a test score of 30 out of 150. Formula: (X ÷ Y) × 100.
Increase / decrease
Measure change between two numbers — a price rise, a discount, a growth rate. Formula: ((To − From) ÷ From) × 100.
Percentage basics
A percentage is just a number expressed as a fraction of 100 — "per cent" literally means "per hundred". So 25% is the same as 25/100, or 0.25. To take a percentage of a number, convert the percent to a decimal and multiply.
Percentage change compares a new value against an original one. A positive result is an increase, a negative result is a decrease. Note that a 50% rise followed by a 50% fall does not return you to the start — because each change is measured against a different base.
This calculator handles decimals and negative numbers, and shows a clear message instead of an error when a value is missing or when a division by zero would occur.
Private by design. Every calculation runs right here in your browser with plain JavaScript. Your numbers are never uploaded, saved or sent anywhere — we never see them.