Percentage Calculator
Calculate percent of a number, ratio percent, and percent change.
Result
Part is what percent of whole?
Percent change
Math tool
Percentage Calculator
Solve common percentage questions instantly.
All tools
Related Tools
Continue with calculators that solve closely related number tasks.
How To Use The Percentage Calculator
The calculator has three independent blocks, and you can use whichever one matches your question. In the first block, type a percentage and a number to find X% of Y — for instance 15 in the percent field and 200 in the of-number field returns 30, which is the answer to "what is 15% of 200". In the second block, enter a part and a whole to discover what proportion the part represents; 25 out of 100 shows as 25%. In the third block, enter an old value and a new value to measure the percent change between them, with the sign telling you whether the figure went up or down. Every result updates as you type, so there is no button to press and no page reload.
The Three Calculations Explained
A percentage is simply a fraction of one hundred: "per cent" means "per hundred", so 15% is the same as the fraction 15/100 or the decimal 0.15. To take a percent of a number, multiply the number by that decimal, which is why 15% of 200 is 0.15 × 200 = 30. To express one number as a percent of another, divide the part by the whole and multiply by 100, so 25 out of 100 is (25 / 100) × 100 = 25%. To measure percent change, subtract the old value from the new value, divide by the old value, and multiply by 100. These three operations cover the overwhelming majority of everyday percentage questions, from shop discounts to exam scores to year-on-year growth.
Worked Percentage Examples
The table below shows each type of calculation with concrete numbers. Read across to see the question, the arithmetic, and the answer the calculator returns.
| Question | Calculation | Result |
|---|---|---|
| 15% of 80 | 0.15 × 80 | 12 |
| 20% of 250 | 0.20 × 250 | 50 |
| 30 is what % of 120 | (30 / 120) × 100 | 25% |
| Change from 80 to 100 | (100 - 80) / 80 × 100 | +25% |
| Change from 60 to 45 | (45 - 60) / 60 × 100 | -25% |
| Price before 20% off (now 96) | 96 / 0.80 | 120 |
Notice that an increase and a decrease of the same size are not symmetric: going up 25% then down 25% does not return you to the start, because each step is measured against a different base.
Worked Example: A Shop Discount
Suppose a jacket costs 80 and the store advertises 15% off. The discount is 15% of 80, or 0.15 × 80 = 12, so you save 12 and pay 68. If you only know the final price of 68 and the 15% discount, you can recover the original with a reverse percentage: divide 68 by 0.85 (because you paid 85% of the original) to get back to 80. The same logic, applied in reverse, lets you add tax or a tip: 20% of a 50 bill is 10, giving a total of 60.
Why This Tool Is Useful
Percentages turn up constantly in daily life, yet they are easy to get wrong under time pressure. This calculator removes the guesswork from the three questions people ask most: how much is a percentage of an amount, what share one figure is of another, and how much something has grown or shrunk. That makes it handy for working out sale prices and VAT, splitting a tip, comparing test scores, tracking a budget line month to month, or sanity-checking a statistic in the news. Because all three blocks are visible at once, you can answer related questions without switching tools or re-entering the same numbers.
Accuracy And Privacy
The calculator uses ordinary floating-point arithmetic in your browser, the same maths your spreadsheet uses, so the results are reliable for everyday figures; for accounting work you may still want to round to two decimal places yourself. Crucially, everything runs locally on your device. Nothing you type is uploaded, saved, or sent to any server, the page works offline once it has loaded, and there is no account or sign-up. Your numbers stay entirely private to you.
FAQ
What is the formula for percentage change?
Percentage change is (new value minus old value) divided by the old value, multiplied by 100. For example, going from 80 to 100 gives (100 - 80) / 80 = 0.25, which is a 25% increase. Always divide by the old value, not the new one, because the original amount is your point of comparison.
How do I tell an increase apart from a decrease?
If the new value is larger than the old value the change is positive and counts as an increase; if the new value is smaller the result is negative and counts as a decrease. A move from 50 to 60 is a 20% increase, while a move from 60 to 50 is a 16.67% decrease. The two are not equal because each is measured against a different starting amount.
How do I work out a reverse percentage?
A reverse percentage finds the original number before a percentage was added or removed. If a price is 120 after a 20% increase, divide by 1.20 to get the original 100. If a sale price of 90 already has 10% off, divide by 0.90 to recover the original 100. Divide rather than subtract the same percentage, because the percentage was applied to the original amount, not the final one.
What is the difference between percent and percentage points?
A percentage point is the plain arithmetic gap between two percentages, while a percent change describes that gap relative to the starting value. If an interest rate rises from 5% to 7%, that is a 2 percentage point increase but a 40% increase, because 2 / 5 = 0.40. Mixing the two is a common source of misleading statistics.
Does this calculator send my numbers anywhere?
No. Every calculation runs locally in your browser using plain arithmetic, so the values you type are never uploaded, logged, or stored on a server. You can use it offline once the page has loaded, and nothing you enter leaves your device.