Calculate percent of a number, percentage increase/decrease, and percentage change in seconds—right in your browser.
47.50 × 0.18 = 8.55). For % change, both the absolute difference and the relative percentage are shown so you can see whether you're looking at a 4-point swing or a 25% jump.Percentages turn up everywhere — interest rates, sales tax, restaurant tips, exam scores, stock returns, A/B-test lift, body-fat ratios. The arithmetic is simple but easy to flub under time pressure, especially when the question shifts between "percent of," "percent off," and "percent change" — three different formulas that look alike on the page. A dedicated calculator removes the guesswork and surfaces the working so you can verify the math.
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| Mode | Question it answers | Formula | Example |
|---|---|---|---|
| Percent of | What is X% of Y? | Y × (X / 100) |
18% of 47.50 = 8.55 |
| Percent expressed | X is what % of Y? | (X / Y) × 100 |
47 of 60 = 78.33% |
| Percent change | What's the % change from X to Y? | ((Y − X) / X) × 100 |
1.2 → 1.5 = +25% |
| Add percent | X plus Y% | X × (1 + Y/100) |
129 + 8.875% = 140.45 |
| Subtract percent | X minus Y% | X × (1 − Y/100) |
89 − 30% = 62.30 |
Note that "percent of" and "subtract percent" are different views of the same arithmetic: 30% off $89 is $89 × 0.70 = $62.30, which is the same as "what is 70% of 89?" — the calculator picks whichever framing matches how the question was asked.
For estimates without a calculator, the following shortcuts cover most everyday cases. They work because 10% is the easy anchor — divide by 10 — and every other percentage builds from there.
| Percent | Shortcut | Worked example on $87 |
|---|---|---|
| 1% | Move the decimal two places left | $0.87 |
| 5% | Half of 10% | $4.35 |
| 10% | Move the decimal one place left | $8.70 |
| 15% | 10% + half of 10% | $13.05 |
| 18% | 20% − one-tenth of 20% | $15.66 |
| 20% | Double the 10% value | $17.40 |
| 25% | Divide by 4 | $21.75 |
| 33⅓% | Divide by 3 | $29.00 |
| 50% | Divide by 2 | $43.50 |
| 75% | Three-quarters (subtract 25% from the total) | $65.25 |
For tipping, the 15/18/20% trio is the most useful: find 10% by moving the decimal, then add half of that for 15%, double it for 20%, or land between the two for 18%.
A percentage point is the arithmetic difference between two percentages; a percentage change is the relative difference. If an unemployment rate moves from 4% to 5%, that's an increase of 1 percentage point (5 − 4) but a 25% increase in the rate itself (1 ÷ 4 = 0.25). Journalists, central banks, and pollsters use "pp" (or "p.p.") explicitly because confusing the two can make a small policy shift sound dramatic — or vice versa. When in doubt, ask: are we talking about the gap between two rates, or how much one rate grew?
Percent change is ((new − old) / old) × 100. The denominator is always the original value because you're measuring the shift relative to where you started. Revenue rising from $50 to $60 is a 20% increase: (60 − 50) / 50 = 0.2. Note that the result is not symmetric — going from 50 to 60 is +20%, but going back from 60 to 50 is −16.7%, because the denominator changed.
No — stacked percentage discounts multiply, they don't add. On a $100 item, 50% off brings it to $50; an additional 20% off the discounted price brings it to $40. That's 60% off the original, not 70%. The formula is (1 − d₁) × (1 − d₂) = (1 − 0.50) × (1 − 0.20) = 0.40, so you pay 40% of the original price. Order doesn't matter — 20% off then 50% off lands on the same $40 — but the discounts compound, not sum.
Not reliably. Averaging the percentages (the arithmetic mean, or AAGR) overstates the true annualized rate whenever growth is volatile, because it ignores compounding. The correct metric is CAGR (compound annual growth rate): (End / Start)^(1/n) − 1, where n is the number of years. A portfolio that returns +50%, −50%, +50% over three years has an arithmetic average of +16.7% but a CAGR of about −2.1% — you actually lost money. CAGR equals the arithmetic mean only when every year has the identical return.
They share the numerator (selling price minus cost) but use different denominators. Markup divides by cost: (Price − Cost) / Cost. Margin divides by selling price: (Price − Cost) / Price. A $70 cost sold for $100 has a $30 gross profit, which is a 42.9% markup ($30 / $70) but a 30% margin ($30 / $100). Because cost is always lower than price (assuming you're profitable), markup % is always higher than margin % for the same transaction. Mixing them up is a common pricing error — a "40% markup" only delivers a 28.6% margin.
Three distinct operations on two different bases. Percent of asks for a share of a single value: "20% of 50" = 10. Percent off subtracts that share from the base: "20% off 50" = 50 − 10 = 40. Percent change compares two values: "from 40 to 50" = +25%. The trap: "50 is 25% more than 40" and "40 is 20% less than 50" describe the same pair, but the percentages differ because the denominator switches.
To remove a percent that was added (tax, markup), divide by (1 + p/100). A $108 receipt that includes 8% sales tax came from $108 / 1.08 = $100 pre-tax. To remove a percent that was subtracted (discount), divide by (1 − p/100). An item on sale for $40 at 20% off had a $40 / 0.80 = $50 list price. The common mistake is adding back the same percentage you took off — 20% off $50 is $40, but 20% added to $40 is only $48.
Results display to two decimal places by default, which matches currency conventions. Internally the calculation is full-precision (JavaScript double), so a chain of operations isn't accumulating rounding error in the background. If you need a different precision — say, four decimals for a scientific or engineering use case — copy the displayed value and round to your required figure, or read the unrounded value from the formula breakdown shown beneath the result.
No. The percentage calculator runs entirely in client-side JavaScript — no inputs, no results, and no analytics of the numbers you enter are sent to xconvert servers. The page works offline once it has loaded, which is also why the answer appears instantly with no network round-trip.