Percentage Calculator — Find %, Increase, Decrease & More
Calculate percentages in 6 ways online free — find what percentage X is of Y, calculate percentage increase or decrease, find original value before percentage change, and more. No sign-up required.
Last updated: June 2026
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About this tool
Every percentage question, answered
Percentages come up everywhere — discounts and sales tax when shopping, tips at restaurants, interest on loans, grades at school and growth figures at work. This percentage calculator brings the six most common percentage questions into one place, each on its own tab so you never have to remember which formula to use.
The first two modes are the classics: what is X% of Y (for finding a portion of a total) and X is what percent of Y (for expressing one number as a percentage of another). The percentage change mode compares an old value to a new one and tells you the increase or decrease — ideal for tracking price moves, salary changes or statistics.
For money tasks, add X% to Y applies a markup or tax to a base amount, while subtract X% from Y applies a discount and shows the final price. Finally, the reverse percentage mode answers "X is Y% of what number?" — perfect for working back to an original price before a discount, or a total from a known share. Every mode shows the exact formula it used, so the tool doubles as a way to learn the maths, not just get the answer. All calculations run privately in your browser.
How it works
Three quick steps — no account, nothing uploaded to a server.
Choose a mode
Pick the percentage question you need to answer.
Enter your numbers
Type the values — the result updates as you type.
Copy the answer
See the formula and copy the result with one click.
FAQ
Frequently asked questions
How do I calculate a percentage of a number?
To find X% of Y, multiply Y by X and divide by 100. For example, 20% of 150 is (20 ÷ 100) × 150 = 30. Use the first tab, enter the percentage and the number, and the answer appears instantly along with the formula so you can see exactly how it was worked out.
How do I work out what percentage one number is of another?
Divide the part by the whole and multiply by 100. For example, 45 out of 200 is (45 ÷ 200) × 100 = 22.5%. The second tab does this for you — enter the two numbers and it returns the percentage with the formula shown.
How do I calculate percentage increase or decrease?
Subtract the original value from the new value, divide by the original, and multiply by 100. A move from 80 to 100 is ((100 − 80) ÷ 80) × 100 = 25% increase; a move from 100 to 80 is a 20% decrease. The percentage-change tab labels the result as an increase or decrease automatically.
What is reverse percentage and when do I use it?
Reverse percentage finds the original number when you only know a part and what percentage it represents. If 30 is 20% of something, the original is (30 ÷ 20) × 100 = 150. It's useful for working back to a pre-discount price or a total from a known share — use the 'X is Y% of what?' tab.
Can I use this for discounts, tax and markup?
Yes. Use the 'Add X% to Y' tab for adding sales tax or a markup to a price, and the 'Subtract X% from Y' tab for applying a discount. Each shows the final amount and the formula, so it's quick for shopping, invoicing or pricing decisions.
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