What is a percentage?
A percentage is simply a way of expressing a number as a fraction of 100. The word comes from the Latin per centum, meaning “by the hundred.” When you say 15%, you mean 15 out of every 100. Percentages make it easy to compare quantities on a common scale — which is why they show up everywhere from tips and discounts to interest rates, tax, and test scores.
How to calculate a percentage of a number
To find a percentage of a number, multiply the number by the percentage and divide by 100. The formula is: result = (percentage × value) ÷ 100. For example, to find 15% of 200, calculate (15 × 200) ÷ 100 = 30. The calculator above does this instantly — enter the percentage and the value, and the answer updates as you type.
How to find what percentage one number is of another
Sometimes you have two numbers and want to know the percentage relationship between them — for instance, “30 is what percent of 200?” Divide the first number by the second and multiply by 100: (30 ÷ 200) × 100 = 15%. Switch to the “X is what % of Y” tab in the calculator to do this without any manual math.
Everyday uses for a percentage calculator
- Tips: quickly work out a 15% or 20% tip on a bill.
- Discounts: find the sale price after a percentage off.
- Tax: add sales tax or work out a tax amount.
- Grades: convert a score like 42/50 into a percentage.
- Finance: estimate interest, commission, or growth.
Why use this calculator
It is free, loads instantly, and works on any device with a clean light or dark theme. There is no sign-up, no clutter, and the tool is never buried under ads — just type your numbers and get the answer. It runs entirely in your browser, so nothing you enter is sent anywhere.