How to Calculate Percentage
Master percentages with simple formulas and real-world examples
⚡Quick Answer
Basic formula: (Part ÷ Whole) × 100. Find X% of Y: (X ÷ 100) × Y. Percentage increase: ((New − Old) ÷ Old) × 100. To convert a decimal to percent, multiply by 100.
Step-by-Step Guide
Use the Basic Percentage Formula
The core formula is: Percentage = (Part ÷ Whole) × 100. Example: you scored 42 out of 50 on a test. (42 ÷ 50) × 100 = 84%.
Find a Percentage of a Number
To find X% of Y, use: (X ÷ 100) × Y. Example: 20% off a $60 item. (20 ÷ 100) × 60 = $12 discount. You pay $48.
Calculate Percentage Increase or Decrease
Formula: ((New Value − Old Value) ÷ Old Value) × 100. Example: price went from $80 to $100. ((100 − 80) ÷ 80) × 100 = 25% increase. If the result is negative, it's a decrease.
Convert Between Fractions, Decimals, and Percentages
Fraction to %: divide numerator by denominator, then × 100. (3/4 = 0.75 × 100 = 75%). Decimal to %: multiply by 100 (0.35 = 35%). % to decimal: divide by 100 (45% = 0.45).
Frequently Asked Questions
What is the easiest way to calculate a percentage in my head?
Find 10% first by moving the decimal one place left, then multiply or combine. For 15%: find 10% + half of that (5%) and add them together.
How do I calculate what percentage one number is of another?
Divide the part by the whole, then multiply by 100. Example: 15 is what percent of 60? (15 ÷ 60) × 100 = 25%.
How do I reverse a percentage — find the original price before a discount?
Divide the sale price by (1 − discount rate). Example: item costs $68 after a 15% discount. $68 ÷ 0.85 = $80 original price.