TOOLEvery kind of percentage, one place
This calculator handles the three percentage questions people actually ask: how much a percentage of a number is, what proportion one number is of another, and how much something changed in percentage terms. Type into any field and the answer updates instantly — no equals button, no page reload.
The formulas behind it
- Percent of a number: (percent ÷ 100) × number. So 20% of 150 = 30.
- What percent of: (part ÷ whole) × 100. So 30 of 150 = 20%.
- Percentage change: ((new − old) ÷ old) × 100. A move from 150 to 180 is a +20% change; from 180 to 150 is −16.7%.
Everyday uses
Percentages show up everywhere: working out a tip or sales tax, checking a discount, reading a test score, comparing price changes, or tracking growth. Having the right formula applied automatically removes the guesswork — and the mental math.
Worked examples you can follow
Seeing the math on real numbers makes it stick. Here are four everyday percentage problems and exactly how they're solved:
- A 15% tip on a $64 bill: 0.15 × 64 = $9.60, for a $73.60 total. The tip calculator also splits it per person.
- A jacket marked 30% off $120: 0.30 × 120 = $36 off, so you pay $84. Stack coupons and tax with the discount calculator.
- Scoring 47 out of 60 on a test: 47 ÷ 60 × 100 = 78.3%.
- Traffic rising from 1,200 to 1,560 visits: (1,560 − 1,200) ÷ 1,200 × 100 = +30%.
Percentage points vs percent — and other traps
A common mistake is confusing a percentage change with percentage points. If a rate goes from 5% to 8%, that's a rise of three percentage points but a 60% increase in relative terms — both are correct answers to different questions. Another trap: percentage change isn't symmetric. Going from 100 to 150 is a 50% increase, but going back from 150 to 100 is only a 33.3% decrease, because the starting point (the denominator) changed.
Once you're comfortable with the basics, the same math powers sales tax, profit margins and compound interest. For a plain-English walkthrough with more examples, read how to calculate a percentage.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. For example, 20% of 150 is 0.20 × 150 = 30.
How do I work out what percent one number is of another?
Divide the part by the whole and multiply by 100. For example, 30 out of 150 is 30 ÷ 150 × 100 = 20%.
How is percentage increase or decrease calculated?
Subtract the old value from the new value, divide by the old value, and multiply by 100. A rise from 150 to 180 is (180 − 150) ÷ 150 × 100 = 20% increase.