How to use Percentage Calculator
- Choose the calculator that matches your question and type your numbers. The answer appears as you type.
- What is X% of Y? finds a share of a number, for example 15% of 200.
- X is what percent of Y? shows how big one number is compared with another.
- Percentage change tells you how much a value went up or down. Increase or decrease adds or removes a percentage, such as a discount or tax.
About this tool
Percentages are used for discounts, sales tax, tips, grades, interest, statistics and prices. This page does the four most common calculations without a calculator.
Percentage change is calculated as (new − old) ÷ old × 100. A result of 25% means the new value is a quarter bigger than the old one, and −25% means it is a quarter smaller. A change from 0 cannot be expressed as a percentage, because dividing by zero is not possible. If the starting number is negative, the change is measured against its size (absolute value), so the sign still shows the direction.
Remember that increasing a number by a percentage and then decreasing the result by the same percentage does not bring you back to the start. For example, 100 plus 20% is 120, and 120 minus 20% is 96. Results are shown with up to 10 decimal places.
Privacy: This tool runs in your browser. What you type or choose is not sent to a server by this website.
Common questions
How do I calculate a discount?
Use “Increase or decrease a number”. Enter the price and the discount percentage; the decrease result is the new price.
Why is the percentage change different when I swap the numbers?
Because the change is always measured against the starting value. Going from 80 to 100 is +25%, but going from 100 to 80 is −20%.
Can I use decimals and negative numbers?
Yes. Use a decimal point, for example 12.5.
Why does it say the result is undefined?
Dividing by zero has no answer, so questions such as “what percent of 0” or “change from 0” cannot be calculated as a percentage.