// The basics
Understanding Percentages
A percentage is a way of expressing a number as a fraction of 100. The word itself comes from the Latin "per centum" — meaning "per hundred." Percentages are one of the most practical tools in everyday math, used for everything from calculating discounts and taxes to understanding statistics and grades.
Despite being fundamental, percentage calculations trip people up because there are several different types of questions you might need to answer — and they each require a slightly different approach.
// How it works
The Three Formulas
What is X% of Y? Multiply Y by X divided by 100. For example, 15% of 200 = 200 × (15 ÷ 100) = 30.
X is what percent of Y? Divide X by Y and multiply by 100. For example, 30 is what percent of 200? = (30 ÷ 200) × 100 = 15%.
Percentage change from A to B: Subtract A from B, divide by A, multiply by 100. For example, change from 80 to 100 = ((100 - 80) ÷ 80) × 100 = 25% increase.
// FAQ
Frequently Asked Questions
What's the difference between percentage and percentage points?
A percentage point is the arithmetic difference between two percentages. If interest rates go from 2% to 5%, that's a 3 percentage point increase — but a 150% relative increase. These are often confused in news and finance reporting.
How do I calculate a discount?
Use mode 1: enter the discount percentage and the original price. The result is the amount you save. Then subtract from the original price to get the final price. For example, 25% off $80 = $20 saved = $60 final price.
How do I calculate a grade percentage?
Use mode 2: enter your score as X and the total possible points as Y. The result is your percentage score. For example, 43 out of 50 = (43 ÷ 50) × 100 = 86%.
Can I calculate a negative percentage change?
Yes — if the "To" number is smaller than the "From" number, the result will automatically show as a negative percentage, indicating a decrease. For example, from 100 to 75 = -25%.