Three modes: find a percentage of a number, find what percent one number is of another, or calculate percentage change.
This is a fast, no-fuss percentage calculator with three distinct modes: work out a percentage of a number (X% of Y), find what percentage one number is of another (X is what % of Y), and calculate the percentage change between an original and a new value. Results appear instantly as you type, complete with the underlying formula so you can see exactly how each answer is derived.
It is handy whenever you need a quick percent answer without reaching for a spreadsheet or doing the arithmetic by hand. People use it to:
Everything runs locally and in-browser. The numbers you enter never leave your device — nothing is uploaded, stored, or shared, so it is private by default.
Multiply the number by the percentage and divide by 100. For example, 15% of 200 = 200 × 15 ÷ 100 = 30. Use the "X% of Y" mode above and enter the percentage and the number for an instant answer.
Divide X by Y, then multiply by 100. For example, 30 out of 200 is (30 ÷ 200) × 100 = 15%. The "X is what % of Y" mode does this for you the moment you enter both values.
Subtract the original from the new value, divide by the original, then multiply by 100. From 80 to 100 that is ((100 − 80) ÷ 80) × 100 = 25% increase. Use the "% Change" mode and enter the original then the new value.
It uses the same formula as an increase, but a smaller new value gives a negative result. From 100 to 80 that is ((80 − 100) ÷ 100) × 100 = −20%, which the "% Change" mode shows as a percentage decrease.
Percentage change = ((New − Original) ÷ Original) × 100. A positive result is an increase and a negative result is a decrease. The "% Change" mode colours the answer green for increases and red for decreases.
If you know a value is X% of an unknown total, divide that value by X and multiply by 100. For example, if 30 is 15% of a number, the original is (30 ÷ 15) × 100 = 200. The "X is what % of Y" mode helps you check the relationship between the part and the whole.
A percentage point is the arithmetic difference between two percentages. If a rate moves from 10% to 15%, that's 5 percentage points but a 50% relative increase.