Percentage calculator
Four common percentage questions answered as you type.
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How to use it
Step 1
Find the box that matches your question.
Step 2
Type the two numbers. The answer updates as you type.
Step 3
Change the numbers to try other cases.
Step 4
Copy the answer from the result line.
About this tool
Percentages come up in discounts, marks, interest, tax, growth and salary changes. Each question has a different formula, which is easy to mix up, so this page shows the four most common ones side by side.
X percent of Y is X divided by 100, multiplied by Y. For "what percent", divide the part by the whole and multiply by 100. Percentage change is the difference divided by the starting value. To increase a number by X percent, multiply it by 1 plus X over 100; to decrease it, multiply by 1 minus X over 100.
For example, 20% of 150 is 30. A rise from 50 to 80 is a 60% increase, but a fall from 80 to 50 is only a 37.5% decrease, because the starting value is different. All calculations are done in your browser.
Questions
How do I calculate a discount?
Use the last box: enter the discount percent and the price, and read the decrease result.
Why is a 60% increase not reversed by a 60% decrease?
The second percentage is taken from a larger number. Going from 50 to 80 is up 60%, but 80 back to 50 is down 37.5%.
How do I find marks as a percentage?
Use the second box: enter your marks as X and the total marks as Y.
Can I use decimals and negative numbers?
Yes. Decimals work in every box.