Percentage Calculator

Covers three common percentage calculations in one tool: what X% of a number is, what percentage one number is of another, and the percentage increase or decrease between two values.

Click one of the three mode buttons — "X% of Y", "X is what % of Y", or "% increase/decrease" — then fill in the fields for that mode. The result updates immediately as you type.

"X% of Y" with the defaults 10% and 50 gives 10% × 50 = 5. "X is what % of Y" with, say, 25 as the value and 200 as the total gives (25 ÷ 200) × 100 = 12.5%. "% increase/decrease" with the defaults from 50 to 60 gives ((60 − 50) ÷ 50) × 100 = 20%, a 20% increase.

X% of Y = Y × (X ÷ 100). X is what percent of Y = (X ÷ Y) × 100. Percentage change from A to B = ((B − A) ÷ A) × 100 — positive for an increase, negative for a decrease.

A negative result means a decrease, not an error — going from 60 to 50 gives ((50 − 60) ÷ 60) × 100 ≈ −16.67%, a 16.67% decrease. Note that a percentage decrease and the percentage increase needed to reverse it aren't the same number: a 20% increase from 50 to 60 requires a 16.67% decrease, not 20%, to get back to 50.

Each mode is independent and doesn't carry values over from the others, so switching modes doesn't chain a calculation. The "is what percent" mode requires a non-zero total, since dividing by zero has no defined percentage.

These are the standard percentage formulas taught in arithmetic and used across finance, statistics and everyday calculations worldwide. Calculations run locally in your browser; the values you enter are never uploaded.