How percentage calculations work
Finding P% of a number
To find a percentage of a number, convert the percentage to a decimal (divide by 100) and multiply:
Result = Number × (Percentage ÷ 100)
Example: 15% of 200 = 200 × 0.15 = 30
Finding what percent X is of Y
Divide the part by the whole, then multiply by 100:
Percentage = (Part ÷ Whole) × 100
Example: 30 is what percent of 120? = (30 ÷ 120) × 100 = 25%
Calculating percentage change
Subtract the original value from the new value, divide by the original, then multiply by 100. A positive result is an increase; negative is a decrease:
% Change = ((New − Original) ÷ Original) × 100
Example: from 80 to 100 = ((100 − 80) ÷ 80) × 100 = +25%
Frequently asked questions
How do I calculate what percent one number is of another?
Divide the part by the whole and multiply by 100. For example, 30 is what percent of 120? Divide 30 by 120 to get 0.25, then multiply by 100 to get 25%.
How do I find a percentage of a number?
Multiply the number by the percentage divided by 100. For example, 15% of 80 equals 80 times 0.15, which is 12.
How do I calculate a percentage increase or decrease?
Subtract the original value from the new value, divide by the original value, then multiply by 100. A positive result means an increase; a negative result means a decrease.
What is 20% of 500?
20% of 500 is 100. To calculate: 500 times 0.20 equals 100.
How do I reverse a percentage to find the original number?
Divide the known value by the percentage expressed as a decimal. For example, if 60 is 75% of a number, divide 60 by 0.75 to get 80.
Estimates only. Results are for general information and are not financial or mathematical advice.