Everyday formula
Percentage Formula
Learn the percentage formula, how to find X% of a number, how to reverse a percentage, and how the variables relate.
Formula
Percentage amount = (percentage ÷ 100) × base valueWhat the formula means.
Convert the percentage to a decimal by dividing by 100, then multiply by the base value. The same relationship can be rearranged to find the percentage or the original value.
A percentage is a ratio per 100.
Use the same base value throughout the calculation.
Percentage change and percentage points are different ideas.
Variables.
pPercentage
The rate expressed out of 100.
BBase value
The whole amount the percentage is applied to.
APercentage amount
The resulting part of the base value.
Worked example.
Find 20% of 150
- 20 ÷ 100 = 0.20
- 0.20 × 150 = 30
Try your own numbersPercentage Calculator
↗Common mistakes.
- Multiplying by 20 instead of 0.20.
- Using the final value as the base when the question refers to the original value.
- Confusing “20% of 150” with “20 is what percent of 150.”
Quick questions.
How do I turn a percentage into a decimal?
Divide by 100. For example, 7.5% becomes 0.075.
How do I find what percent one number is of another?
Divide the part by the whole, then multiply by 100.