How to calculate percentages
A percentage is a number expressed as a fraction of 100. To find X% of Y, multiply Y by X and divide by 100. To find what percent X is of Y, divide X by Y and multiply by 100. Percentage change compares an old and a new value: (new − old) ÷ old × 100.
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Percentage calculator: frequently asked questions
How do I calculate 20% of a number?
Multiply the number by 20 and divide by 100. For example, 20% of 150 is 150 × 20 ÷ 100 = 30.
How do I calculate a percentage increase or decrease?
Subtract the old value from the new one, divide by the old value and multiply by 100. A positive result is an increase and a negative one is a decrease.
How do I add a percentage to a price?
Multiply the price by 1 plus the percentage divided by 100. For example, 200 plus 15% is 200 × 1.15 = 230. To subtract a percentage, use 1 minus the percentage instead.