How to Calculate Percentages
A percentage is a way of expressing a number as a fraction of 100. The word "percent" comes from the Latin "per centum," meaning "by the hundred." Percentages are used in everyday life for discounts, taxes, tips, statistics, and financial calculations.
Basic Percentage Formula
To find X% of Y: multiply Y by X and divide by 100. For example, 25% of 200 = 200 × 25 ÷ 100 = 50.
Percentage Change Formula
To calculate the percentage change between two values: ((New Value - Old Value) / Old Value) × 100. A positive result indicates an increase, while a negative result indicates a decrease.
Common Percentage Conversions
| Fraction | Decimal | Percentage |
|---|
| 1/2 | 0.5 | 50% |
| 1/3 | 0.333 | 33.3% |
| 1/4 | 0.25 | 25% |
| 1/5 | 0.2 | 20% |
| 1/8 | 0.125 | 12.5% |
| 1/10 | 0.1 | 10% |
Frequently Asked Questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 20% of 150 = 150 × 20 ÷ 100 = 30.
How do I calculate percentage change?
Subtract the old value from the new value, divide by the old value, and multiply by 100. Formula: ((New - Old) / Old) × 100.
What is the difference between percentage increase and decrease?
Percentage increase means adding a percentage to the original value, while decrease means subtracting. For example, 100 increased by 20% = 120, decreased by 20% = 80.