How to Calculate Percentages
Percentages are one of the most common calculations in everyday life — from tips and discounts to tax, interest and grades. Here are the key formulas:
X% of Y = ?
Multiply Y by X and divide by 100. Example: 15% of 200 = (15 × 200) ÷ 100 = 30.
Percentage Change
((New − Old) ÷ Old) × 100. A positive result is an increase; negative is a decrease.
Adding a Percentage
Original × (1 + percentage/100). Adding 20% to 100 = 100 × 1.20 = 120.
Removing a Percentage
Original × (1 − percentage/100). Removing 20% from 100 = 100 × 0.80 = 80.
Common Percentage Examples
- 15% tip on $50 = $7.50
- 20% off $120 = $96
- Tax of 8.5% on $200 = $17 tax, $217 total
- Score of 42/50 = 84%
FAQs
How do I calculate a percentage on a calculator?
To find X% of Y: enter Y × X ÷ 100. Most smartphones also have a % button. Our online calculator above handles all percentage types automatically.
What's the difference between percentage and percentage points?
Percentage points refer to the absolute difference between two percentages. If a rate goes from 5% to 8%, that is a 3 percentage point increase, but a 60% percentage increase.
How do I calculate percentage increase?
Use the formula: ((New Value − Old Value) ÷ Old Value) × 100. For example, going from 80 to 100 is ((100−80)÷80)×100 = 25% increase.