Three common percentage calculations
Percentages show up everywhere — discounts, exam scores, tax rates, statistics. This tool covers the three calculations people search for most often: finding a percentage of a number, finding the percentage change between two values, and reversing a percentage to find an original amount.
Quick reference formulas
- Percentage of a number: (percentage ÷ 100) × number
- Percentage change: ((new − original) ÷ original) × 100
- Reverse percentage: value ÷ (percentage ÷ 100)
Frequently asked questions
How do I calculate a percentage of a number?
To find a percentage of a number, divide the percentage by 100 and multiply by the number. For example, 20% of 150 is (20 ÷ 100) × 150 = 30.
How do I calculate percentage change?
Percentage change is calculated by subtracting the original value from the new value, dividing by the original value, and multiplying by 100. A positive result is an increase, and a negative result is a decrease.
What is a reverse percentage calculation?
A reverse percentage calculation finds the original value before a percentage was applied. For example, if 30 is 20% of a number, the original number is found by dividing 30 by 0.20, which equals 150.