A% of B
result = (A ÷ 100) × B
Percentage Calculator — % of a number, ratio, and change
Do the three most common percentage calculations in one place: A% of B, A is what % of B, and percent change. With formulas, examples, and FAQ.
Percentage Calculator
Four common percentage operations in one place.
What is A% of B?
A is what percent of B?
Percent change from A to B
Price after discount
A percentage is simply a ratio out of 100
Percentage math is one of the most common everyday calculations. This tool instantly handles three operations on one screen: (1) A% of a value, (2) what percent one value is of another, and (3) how much a value went up or down (percent change).
Formulas
A is what % of B
result = (A ÷ B) × 100
Percent change
result = ((To − From) ÷ |From|) × 100
How to use
- Pick the type you need (percent of, ratio, or change).
- Enter the two numbers and the result appears instantly.
- Use it for discounts, test scores, price changes, and more.
Frequently asked questions
How do I convert 20% to a decimal?
Divide the percent by 100. 20% = 20 ÷ 100 = 0.2.
What if the starting value is 0 for percent change?
Percent change is undefined when the starting value is 0 (you cannot divide by zero). Use the absolute change instead.
How do I calculate a discount?
Use 'percent change' with the original and sale price to get the decrease, or use 'A% of B' to take the discount percent off the original.
This tool is for general arithmetic. For official figures such as taxes or finance, confirm with the relevant authority.