Percentage Calculator
Work out X% of a number, a percentage increase or decrease, or the change between two values.
What this calculates
A percentage is a fraction of one hundred. 20% means 20 out of every 100, so 20% of 150 is 30. This calculator answers the four everyday percentage questions: taking a percentage of a number, increasing or decreasing a number by a percentage, and measuring the change between two numbers as a percentage.
Formula
X% of Y = Y × X ÷ 100 Y + X% = Y × (1 + X ÷ 100) Y − X% = Y × (1 − X ÷ 100) change A → B = (B − A) ÷ |A| × 100
Example
20% of 150: multiply 150 by 20 and divide by 100 — the answer is 30. A price rising from 150 to 180 is a change of (180 − 150) ÷ 150 × 100 = 20%.
Frequently asked questions
What is the difference between percentage change and percentage points?
If a rate moves from 10% to 12%, it rose by 2 percentage points, but by 20% in relative terms — the 2-point rise is a fifth of the original 10%. This calculator's change mode gives the relative figure.
Why can't the starting value be zero in change mode?
Percentage change divides by the starting value. From zero, any increase would be infinite — there is no meaningful percentage, so the calculator asks for a non-zero start instead of showing a misleading number.
Does a 20% increase then a 20% decrease get back to the start?
No. 100 increased by 20% is 120; 120 decreased by 20% is 96. The decrease applies to the larger number, so you end up below where you started.