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.
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.
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.
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. For dedicated tax math with a remove-tax option, try our Sales Tax Calculator.
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%.