Percentage Calculator — 3 Formulas, Instant Results
Calculate any percentage instantly — find X% of a number, find what percentage one number is of another, or calculate the % change between two values.
Percentage calculator
The three percentage formulas
1. What is X% of Y?
Formula: (X ÷ 100) × Y. Example: What is 15% of 340? → (15 ÷ 100) × 340 = 51. Used for: calculating discounts, tips, tax amounts, commission.
2. X is what percentage of Y?
Formula: (X ÷ Y) × 100. Example: 51 is what % of 340? → (51 ÷ 340) × 100 = 15%. Used for: finding what portion one number is of a total.
3. Percentage change
Formula: ((New − Old) ÷ Old) × 100. Example: salary rose from 5,000 to 5,750 → ((5750 − 5000) ÷ 5000) × 100 = 15% increase. Used for: measuring growth, inflation, price changes, salary raises.
Frequently asked questions
Multiply the number by the percentage and divide by 100. Formula: Result = (X ÷ 100) × Y. Example: 15% of 200 = (15 ÷ 100) × 200 = 30.
Divide the first number by the second and multiply by 100. Formula: (A ÷ B) × 100. Example: 30 is what % of 200? = (30 ÷ 200) × 100 = 15%.
Formula: ((New - Old) ÷ Old) × 100. Positive = increase, negative = decrease. Example: 80 to 100 = ((100-80) ÷ 80) × 100 = 25% increase.
Multiply the price by 0.80 to get the final price directly (100% - 20% = 80%). Example: 20% off £150 = £150 × 0.80 = £120. Or: find 20% (£30) and subtract.
Move the decimal point one place to the left. Example: 10% of 450 = 45. For 5%, halve that result = 22.5. For 20%, double the 10% result = 90.