How to calculate percentages
A percentage is just a fraction out of 100. The word "percent" literally means "per hundred," so 25% is the same as 25/100, or 0.25. Almost every percentage problem is one of three types, and this calculator handles all of them.
1. Finding a percentage of a number
Result = (Percent ÷ 100) × Number
To find 20% of 150: 20 ÷ 100 = 0.20, then 0.20 × 150 = 30.
2. Finding what percent one number is of another
Percent = (Part ÷ Whole) × 100
If you scored 45 out of 60: (45 ÷ 60) × 100 = 75%.
3. Percentage increase or decrease
Change % = ((New − Old) ÷ Old) × 100
A price rising from $80 to $100 is a 25% increase. If it fell from $100 to $80 instead, that's a 20% decrease — note the percentages differ because the starting value (the denominator) changes.
Everyday uses
- Tips & discounts: 15% off a $40 item saves $6.
- Grades: 27 correct out of 30 questions is 90%.
- Sales tax: add the tax percent of the price to the price.
- Investing: track gains and losses as percentage change.
Frequently asked questions
How do you calculate a percentage of a number?
Convert the percentage to a decimal by dividing by 100, then multiply by the number. For example, 20% of 150 is 0.20 × 150 = 30.
How do I find what percent one number is of another?
Divide the first number by the second, then multiply by 100. For example, 45 out of 60 is (45 ÷ 60) × 100 = 75%.
How do you calculate percentage increase or decrease?
Subtract the old value from the new value, divide by the old value, and multiply by 100. A rise from 80 to 100 is ((100 − 80) ÷ 80) × 100 = 25% increase. A negative result means a decrease.
What is the difference between percentage points and percent?
A change from 10% to 15% is a 5 percentage-point increase, but a 50% relative increase. Percentage points describe the absolute gap; percent describes the proportional change.