How to Calculate a Percentage (Simple Formulas + Free Tool)
Updated 2026-06-01
Percentages come up everywhere — discounts, tips, taxes, grades, and statistics. Once you know the three core formulas, every percentage question is easy. Or just use the free Percentage Calculator.
1. What is X% of Y?
Multiply: Y × (X ÷ 100).
Example: 15% of 200 = 200 × 0.15 = 30.
2. X is what percent of Y?
Divide and multiply by 100: (X ÷ Y) × 100.
Example: 30 is what percent of 200? (30 ÷ 200) × 100 = 15%.
3. Percentage increase or decrease
Use the change over the original: ((new − old) ÷ old) × 100.
Example: from 200 to 230 → (30 ÷ 200) × 100 = 15% increase. A negative result is a decrease.
Try it instantly
The Percentage Calculator does all three for you. For shopping math, the Discount Calculator and VAT Calculator are purpose-built.
Frequently asked questions
How do I add a percentage to a number? Multiply by (1 + percent ÷ 100). Adding 15% to 200 → 200 × 1.15 = 230.
Is my data uploaded? No. Everything calculates in your browser.