About percentage calculator
Percentages show up in discounts, marks, interest, tax and growth figures. Most questions fall into three shapes, and knowing which one you have makes the answer easy to check.
The three common questions
- What is X% of Y? Multiply: Y × X ÷ 100. 15% of 2,400 is 360.
- X is what percent of Y? Divide: X ÷ Y × 100. 45 out of 60 is 75%.
- What is the percentage change from A to B? (B − A) ÷ A × 100. A price rising from 800 to 920 is a 15% increase.
Percent and percentage points
If an interest rate moves from 8% to 10%, it rose by 2 percentage points, but the rate itself increased by 25 percent. Mixing the two is a frequent source of confusion in news and reports.
A discount trap
A 20% increase followed by a 20% decrease does not return you to the starting value, because the second percentage applies to a bigger number. 100 becomes 120, then 96.
