Percentage Calculator
Find a percentage of a number, work out a percentage, or calculate percentage change.
Result
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Percentages show up in discounts, tips, grades, statistics, and just about every spreadsheet you'll ever touch. This calculator covers the three directions people actually need: finding what a percentage of a number is, working out what percentage one number is of another, and figuring out the percentage change between two values.
Type numbers into any of the fields and the result updates instantly — there's no submit button and nothing is sent anywhere, since the maths runs entirely in your browser.
Which of the three modes you need
| The question you're asking | Mode | Worked example |
|---|---|---|
| What is 15% of 240? | Percentage of a number | 0.15 × 240 = 36 |
| 36 is what percent of 240? | X is what percent of Y | 36 ÷ 240 × 100 = 15% |
| 240 went up to 276 — by what percent? | Percentage change | (276−240) ÷ 240 × 100 = +15% |
The mistake almost everyone makes
A percentage increase and the decrease that undoes it are not the same number. If a $100 item rises 25% to $125, it takes a 20% cut — not 25% — to get back to $100, because the second percentage is measured against the larger base.
The same trap shows up with sale prices, salary changes and stock movements. A 50% loss needs a 100% gain to break even. Whenever a percentage sounds reversible, check which number it was calculated against.
Percentages in everyday situations
- Reverse-solving a total: if 18 is 30% of something, the whole is 18 ÷ 0.30 = 60.
- Tax and tips are just a percentage added on: a 20% tip on $45 is 45 × 1.20 = $54 in one step, rather than calculating the tip then adding it.
- Compound growth is not repeated addition: 10% growth three years running is 1.10³ = 1.331, a 33.1% total rise, not 30%.
- Percentage points are different from percentages — an interest rate moving from 4% to 6% is a 2 percentage-point rise but a 50% relative increase.
Frequently asked questions
- How do I calculate a percentage increase?
- Subtract the original value from the new value, divide by the original value, then multiply by 100. The percentage-change mode does this for you automatically.
- What's the difference between percentage and percentage points?
- A percentage is relative (going from 10% to 20% is a 100% increase), while a percentage point is the raw difference (a 10-point increase). This tool reports the relative percentage change.
- Can this handle negative numbers?
- Yes — enter a negative value and the tool will correctly show a percentage decrease.
- How do I work backwards from a percentage to the original total?
- Divide the part by the percentage expressed as a decimal. If 45 represents 15% of a total, the total is 45 ÷ 0.15 = 300.
- Why doesn't a 20% decrease cancel out a 20% increase?
- Each percentage is applied to a different base. Going up 20% from 100 gives 120; dropping 20% from 120 gives 96, not 100. To reverse a 20% rise you need a 16.67% cut.
Read more on this
- Percentages, discounts and tax: the errors that cost moneyWhy stacked discounts never add up, how to pull tax out of an inclusive total correctly, and why a 20% rise isn't undone by a 20% fall.
- How GST works: slabs, forward vs reverse calculation, and input creditA clear guide to GST slabs, CGST/SGST vs IGST, extracting base price from gross invoices, and how input tax credit prevents cascading taxation.