Percentage Calculator
Calculate percentages instantly — X% of Y, change, what percent, and reverse.
How to Use
- Step 1: Select the calculation mode using the tabs at the top.
- Step 2: Enter your numbers in the input fields.
- Step 3: The result updates instantly — copy it with the Copy button.
About Percentage Calculator
Percentages are one of the most commonly used mathematical concepts in daily life — from calculating discounts and tax to understanding statistics and financial growth. This free online percentage calculator handles the four most common percentage problems in a single, easy-to-use interface.
The X% of Y mode answers questions like "what is 25% of 200?" — simply enter the percentage and the base number. The % Change mode tells you how much a value has grown or decreased, expressed as a percentage — perfect for tracking sales, weight, or stock prices. The X is what % of Y mode lets you find what fraction a number represents of another. The % to Value (reverse) mode works backward: given a result and a rate, it finds the original value.
All calculations happen instantly in your browser with no data sent to any server. Results are displayed with up to 8 decimal places of precision, and you can copy any result to your clipboard with a single click. The tool is fully responsive and works on mobile, tablet, and desktop.
You may also find our Discount Calculator, Fraction Calculator, and Average Calculator helpful.
Frequently Asked Questions
How do I calculate X% of Y?
Divide X by 100 then multiply by Y. Example: 25% of 200 = (25/100) × 200 = 50.
How is percentage change calculated?
Percentage change = ((New − Old) / |Old|) × 100. Positive = increase, negative = decrease.
What does "X is what % of Y" mean?
It finds what percentage X represents of Y. Formula: (X / Y) × 100.
What is reverse percentage?
Given a result and a rate, find the original. If 30 is 20% of something, original = (30/20) × 100 = 150.
Is this tool free?
Yes, completely free with no signup required. All calculations happen in your browser.
Was this tool helpful?
Guide
How to calculate percentages: of a number, change, share and reverse
The Percentage Calculator packs the four questions people most often ask about percentages into one panel. Four tabs sit across the top: 'X% of Y', '% Change', 'X is what % of Y' and '% to Value'. Pick the tab that matches your question, type the numbers, and the answer appears in a box underneath with a Copy button. Each tab keeps its own inputs.
It suits anyone dealing with discounts, price rises, marks, shares of a total or tax-inclusive bills. The tool does the arithmetic only, so the skill lies in choosing the right tab and the right order for old and new values.
Step by step
- Choose a tab: 'X% of Y' for a part of a number, '% Change' for growth or fall, 'X is what % of Y' for a share, '% to Value' to recover an original amount.
- On 'X% of Y', type the percentage in the first box and the base number in the second.
- On '% Change', put the starting figure in Old Value and the finishing figure in New Value.
- On 'X is what % of Y', put the part first and the whole second. On '% to Value', type the known amount, then the percentage it represents.
- Read the grey result box. Click Copy to put the number on your clipboard; for the change and share tabs the percent sign is included.
When this is useful
- Finding the discount amount on a sale price, such as 20% off a ₹2,499 item.
- Measuring how much a salary, rent or monthly bill has risen or fallen.
- Turning marks into a share, for example 36 out of 48.
- Separating the tax from a bill that already includes it, using the reverse tab.
Worked example: A salary revision and a festive-sale price
A monthly salary rising from ₹50,000 to ₹56,500: on '% Change', Old Value 50000 and New Value 56500 give 13%. For a ₹2,499 item at 20% off, 'X% of Y' with 20 and 2499 gives 499.8, so the price paid is 2,499 minus 499.8, or ₹1,999.20. A bill of ₹1,180 that includes 18% tax: '% to Value' with 1180 and 118 returns 1000, so the tax is ₹180.
Tips for better results
- Type the old value first in '% Change'. Swapping the two flips the sign and changes the size of the answer.
- The tool shows up to 8 decimal places and no thousands separators, so round the answer yourself.
- To add or subtract a percentage, work in two steps: find X% of Y, then add it to or subtract it from Y.
- A negative result on '% Change' means a decrease. The tool divides by the size of the old value, so a negative old figure is handled sensibly.
Common mistakes
- Taking the tax rate from a tax-inclusive total. 18% of ₹1,180 is ₹212.40, which is not the tax. The total is 118% of the base price, so use '% to Value' with 1180 and 118 to get ₹1,000, then subtract.
- Expecting a rise and the matching fall to cancel. Going from 50,000 to 56,500 is +13%, but going back from 56,500 to 50,000 is −11.50442478%, because the base changed.
- Confusing percentage points with percent. A rate moving from 10% to 12% is two points but a 20% increase; type 10 and 12 into '% Change' to see the 20%.
- Ignoring zeros. If the base number in a share question, or the percentage in the reverse tab, is 0, or the old value in '% Change' is 0, the tool shows 0 instead of an error. A zero result in those cases means the question has no valid answer.
Your files and privacy
The calculation happens in your browser and the numbers you type are not sent anywhere or stored by this tool. The Copy button only writes the result to your device's clipboard.
Frequently asked questions
What is the difference between the Old Value and New Value boxes?
Old Value is the starting point and New Value is where you ended up. The tool computes (New − Old) divided by the size of Old, times 100. A positive answer is an increase and a negative one is a decrease.
How do I find a percentage of a total, such as marks out of a maximum?
Use 'X is what % of Y'. Enter your marks as X and the maximum as Y. With 36 and 48 the result is 75%.
Can it add GST or another tax to a price?
There is no add-tax button, but you can do it in two steps. Use 'X% of Y' to get the tax amount for your rate and add it to the price. Check the rate that applies to your product, as rates change.
What does the % to Value tab do?
It answers 'a number is some percent of what?'. Enter the known amount and the percentage and it divides one by the other and multiplies by 100, so 30 being 20% of something gives 150.
Why is my result showing many decimal places?
The tool keeps up to 8 decimal places. Many divisions do not end neatly, so round the result to the precision you need, for example two places for money.
Guide reviewed 2026-10-11 by the useToolify team.
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