How to Do Percentages, Step by Step (With Examples)
The word per cent means "out of 100", so a percentage is just a fraction with a denominator of 100. Almost every percentage question is one of three types. Here's each one with a worked example.
Type 1: Finding a percent of a number
Turn the percent into a decimal (divide by 100), then multiply by the number.
Write 25% as a decimal: 25 ÷ 100 = 0.25.
Multiply by the number: 0.25 × 80 = 20.
25% of 80 = 20
Type 2: Finding what percent one number is of another
Write the part over the whole as a fraction, then multiply by 100.
Make a fraction: 15 ÷ 60 = 0.25.
Multiply by 100: 0.25 × 100 = 25%.
15 is 25% of 60
Type 3: Percentage increase or decrease
Find the difference, divide by the original value, then multiply by 100. A positive answer is an increase; a negative one is a decrease.
Difference: 50 − 40 = 10.
Divide by the original: 10 ÷ 40 = 0.25.
Multiply by 100: 0.25 × 100 = 25%.
That's a 25% increase
The same steps work for a decrease — if the new value is smaller, the difference is negative and you get a percentage decrease.
A handy shortcut
To find 10% of a number, just divide by 10. To find 1%, divide by 100. You can build other percentages from these: 30% is three lots of 10%, and 25% is a quarter (divide by 4).
Why percentages matter
Percentages turn up everywhere — test scores, discounts, tips and statistics. They build on place value and dividing, and pair naturally with the grade percentage calculator for turning a score into a percent.
Frequently asked questions
How do I find a percent of a number?
Divide the percent by 100 to get a decimal, then multiply by the number. For example, 25% of 80 = 0.25 × 80 = 20.
How do I calculate percentage change?
Subtract the original from the new value, divide by the original, then multiply by 100. Positive means an increase, negative means a decrease.
Where can I practice with steps shown?
Use the free Percentage Calculator to work out any of the three types with the method shown.