Percentage Calculations Explained

Most everyday percentage problems fall into just three types: finding a percent of a number, finding percent change between two numbers, and finding what percent one number is of another. Once you recognize which type you have, the math is simple.

Percent of a number

To find X% of a number, multiply the number by X and divide by 100. For example, 15% of 80 is (80 × 15) / 100 = 12. This is the formula behind calculating tips, discounts, and taxes.

Percent change (increase or decrease)

Percent change is calculated as ((new value − old value) / old value) × 100. A positive result means an increase; a negative result means a decrease. This is the formula used for things like tracking a price change or a salary raise.

What percent is X of Y

To find what percent one number is of another, divide the part by the whole and multiply by 100: (part / whole) × 100. For instance, 45 out of 60 is (45 / 60) × 100 = 75%. The percent calculator handles all three of these calculation types in one tool.