How percentages actually work
A clear, beginner-friendly walkthrough of percent of, percent change, and the small mistakes that trip almost everyone up.
6 min readReviewed Apr 1, 2026
Quick answer
A percentage is just a fraction with 100 on the bottom. Once you see it that way, every percentage problem becomes a multiplication or division you can do in your head.
The one idea behind every percent
Percent means 'per hundred'. So 25% is just another way of writing 25/100, which simplifies to 1/4. Once you internalize that, the formulas stop feeling like formulas.
Every percent question reduces to one of two operations: multiplying a number by a fraction, or comparing two numbers and writing the result as a fraction of 100.
The three questions you'll ever ask
1. What is X% of Y?
Multiply: (X ÷ 100) × Y. Example: 20% of 80 = 0.2 × 80 = 16.
2. A is what percent of B?
Divide and scale: (A ÷ B) × 100. Example: 16 is what percent of 80? 16/80 × 100 = 20%.
3. What's the percent change from A to B?
(B − A) ÷ A × 100. Example: from 80 to 100 is (100 − 80)/80 × 100 = 25% increase.