Everyday money
Percentage Calculator
Three calculators in one: find a percentage of a number, work out what percent one number is of another, or calculate the percent increase or decrease between two values. Pick a mode, type your numbers, and the answer plus its formula update instantly — all in your browser. Americans reach for percentages dozens of times a week, whether figuring an 18% tip at a Texas diner, a 6% raise on a $58,000 salary, or how much a stock moved between Monday's open and Friday's close. This tool keeps the math honest by showing the exact equation behind every result, so you can sanity-check the number before you act on it.
Choose a mode
Choose a mode and enter your numbers
Switch modes any time — your numbers stay put.
How the percentage calculator works
A percent is just a fraction out of 100. Every mode here is a small rearrangement of the same idea: percent = part ÷ whole × 100. The calculator picks the right form of the equation for whichever mode you select and shows it live below the result.
Formula (active mode)
result = X ÷ 100 × Ywhere: X = the percent, Y = the number you take the percent of
For percent change, a positive answer means an increase and a negative answer means a decrease. The change is always measured relative to the starting value (X).
Notes & assumptions
- Percent change uses the "from" value as the base; if "from" is 0 the change is undefined.
- Results are rounded for display but computed at full precision.
- Calculations are for general information only — verify before relying on them.
The three percentage questions
Nearly every percentage problem you will ever meet is one of three questions in disguise. Figure out which one you are facing and the formula picks itself.
1. What is X% of Y?
Use this when you know the rate and need the amount: a tip, a discount, a commission. The formula is result = X ÷ 100 × Y. Example: 12% of 250 is 12 ÷ 100 × 250 = 30, so a card that pays 12% back on a $250 purchase returns $30.
2. X is what percent of Y?
Use this when you know both amounts and need the rate: a test score, a market share, a savings rate. The formula is percent = X ÷ Y × 100. Example: 60 is 60 ÷ 150 × 100 = 40% of 150, so putting $60 of a $150 windfall into savings means you saved 40% of it.
3. What is the percent change from X to Y?
Use this when a value moved and you need to describe the move: a price hike, a raise, a portfolio swing. The formula is change = (Y − X) ÷ X × 100. Example: from 240 to 300 is (300 − 240) ÷ 240 × 100 = a 25% increase. Note the asymmetry: the same $60 gap run in reverse, 300 down to 240, is (240 − 300) ÷ 300 × 100 = a 20% decrease, because the base you divide by changed.
The calculator's three modes map to these three questions one for one, so if you can name the question, you already know which mode to pick.
Worked example
Say you bought a desk lamp on Amazon for $45 and a coupon takes 15% off. To find the savings, choose What is X% of Y, enter 15 as the percent and 45 as the number: 15 ÷ 100 × 45 = $6.75 off, leaving you paying $38.25. Now imagine your manager says your $48,000 salary is going up to $50,400 next quarter. Switch to Percent change from X to Y, enter 48000 as the "from" and 50400 as the "to": the result is (50,400 − 48,000) ÷ 48,000 × 100 = a 5% raise. Finally, if you scored 43 out of 50 on a practice exam, use X is what percent of Y with 43 and 50 to get 86% — a solid B. The same three formulas cover almost every everyday percentage question you'll run into.
Common scenarios, worked out
These five come up more than any others. Each row shows the setup you would type into the calculator and the answer it returns, so you can use the table as a sanity check or skip the tool entirely.
| Scenario | Setup | Answer |
|---|---|---|
| 20% tip on an $85 dinner | 20 ÷ 100 × 85 | $17.00 tip, $102.00 total |
| 15% discount on a $120 jacket | 15 ÷ 100 × 120 | $18.00 off, you pay $102.00 |
| 8.5% sales tax on a $60 cart | 8.5 ÷ 100 × 60 | $5.10 tax, $65.10 at the register |
| 4% raise on a $65,000 salary | 4 ÷ 100 × 65,000 | $2,600 more, $67,600 new salary |
| 3 wrong out of 40 test questions | 37 ÷ 40 × 100 | 92.5% score |
Two rows land on the same $102 by different routes, a tidy reminder that a percent means nothing without its base. The test-score row uses the second question type (37 correct is what percent of 40), while the other four all use the first. And watch the reverse trap: if you only know the $102 you paid for the jacket, the original price is 102 ÷ 0.85 = $120. Adding 15% back onto $102 gives $117.30, the wrong answer, because the store took its 15% from $120, not from $102.
Percentage points vs. percent
When a rate moves from 5% to 7%, two different-sounding statements are both true: it rose 2 percentage points, and it rose 40 percent. The points version is plain subtraction: 7 − 5 = 2. The percent version treats the old rate as the base: (7 − 5) ÷ 5 × 100 = 40. Same move, two honest descriptions, wildly different emotional weight.
Headlines get this wrong constantly, and usually in the dramatic direction. A savings rate climbing from 5% to 7% APY reported as "rates up 40%" sounds like a windfall; reported as "up 2 points" it sounds like Tuesday. Neither is a lie, but they answer different questions. Whenever a percent change is applied to something that is itself a percent (interest rates, poll numbers, unemployment figures, tax rates), pause and work out which of the two calculations produced the number before you react to it.
Frequently asked questions
How do I find X% of a number?
Divide the percent by 100, then multiply by the number. For example, 20% of 150 is 20 ÷ 100 × 150 = 30. A quick mental shortcut: 10% of any number is just the number with the decimal moved one place left (10% of 150 is 15), so 20% is double that, or 30.
How do I calculate a percentage increase or decrease?
Subtract the starting value from the ending value, divide by the starting value, then multiply by 100. Going from $80 to $100 is (100 − 80) ÷ 80 × 100 = a 25% increase. A negative result means a decrease — $100 down to $80 is (80 − 100) ÷ 100 × 100 = a 20% drop. The change is always measured against where you started.
How do I work out what percent one number is of another?
Divide the part by the whole and multiply by 100. If 30 people out of a 120-person company work remotely, that's 30 ÷ 120 × 100 = 25%. This is how you'd express test scores, survey results, or what share of a budget a single expense represents.
What is the difference between percentage points and percent?
Percentage points measure the raw gap between two rates; percent measures the relative change. Going from 5% to 7% is a rise of 2 percentage points, because 7 − 5 = 2, but a 40% relative increase, because (7 − 5) ÷ 5 × 100 = 40. Use points when comparing rates directly and percent when describing how much something grew from its own starting level.
How do I find the original price before a discount?
Divide the final price by (1 − discount ÷ 100). If you paid $102 after 15% off, the original price was 102 ÷ 0.85 = $120. Adding 15% back onto $102 gives $117.30, which is wrong because the discount was taken from the larger original number, not from the amount you paid.
Why isn't a 50% increase canceled out by a 50% decrease?
Because each percentage is taken from a different base. Start with $100, add 50% and you have $150. Now take 50% off that $150 and you land at $75, not back at $100. The decrease is calculated on the larger number, so it removes more dollars than the increase added.
How do I add a percentage to a number, like sales tax?
Multiply the number by (1 + percent ÷ 100). Adding 8% to a $50 item is 50 × 1.08 = $54. Our Sales Tax Calculator handles dedicated tax math and includes a remove-tax option.
How do I convert a decimal or fraction to a percent?
Multiply a decimal by 100 (0.35 becomes 35%) and add a percent sign. For a fraction, divide the top by the bottom first, then multiply by 100 — 3/8 is 0.375, which is 37.5%.