The percentage formula
Percentage = (Part ÷ Total) × 100. So 45 out of 180 is (45 ÷ 180) × 100 = 25%. This same formula covers exam scores, discounts, growth rates and survey results.
Common percentage calculations
- Percentage increase: ((New − Old) ÷ Old) × 100
- Percentage of a number: (Percentage ÷ 100) × Number
- Reverse percentage: Total ÷ (Percentage ÷ 100) when you know the part and the percentage
Shopping for a sale? The Discount Calculator handles percentage-off pricing directly.
Frequently asked questions
How do I calculate percentage increase or decrease?
Subtract the old value from the new value, divide by the old value, then multiply by 100. A negative result means a decrease.