Free Online Percentage Calculator
Runs 100% in your browser — your numbers never leave your device.
What is X% of Y?
X is what percent of Y?
Percent increase / decrease
About this percentage calculator
Percentages show up everywhere: tips, discounts, tax, interest rates, grade curves, and month-over-month growth. The three calculators above cover the three questions people actually ask. "What is 19% of 199.99?" is the tip-or-tax question. "45 is what percent of 180?" is the progress question — how far through a goal you are. "100 to 125" is the change question — how much something grew or shrank.
One trap to watch: percent change is not the same as percentage points. If a rate moves from 50% to 60%, that is a 10 percentage-point move but a 20% relative increase. Mixing the two up is one of the most common mistakes in business reporting, and the third calculator above uses the relative definition.
Worked examples
The tip question. A $48.50 bill with a 20% tip: 20% of 48.50 = 9.70, so the total is $58.20. At 15% the tip is 48.50 × 15 ÷ 100 = 7.275, which rounds to $7.28. The first box on this page does the arithmetic.
The discount question. A £120 jacket marked 30% off: the discount is 120 × 30 ÷ 100 = £36, so you pay £84. Stacked discounts are sequential, not additive — 20% followed by another 10% off is not 30% off (see the discount calculator for that trap).
The progress question. A student scores 38 out of 50 on a test: (38 ÷ 50) × 100 = 76%. A savings goal of $2,000 with $1,450 saved is (1,450 ÷ 2,000) × 100 = 72.5% funded. The second box answers this one.
The change question. A shop's weekly revenue drops from $1,000 to $850: (850 − 1,000) ÷ 1,000 × 100 = −15%, a 15% decrease. And the trap again: a rate rising from 3% to 5% is a 2 percentage-point increase but a 66.7% relative increase — always check which one a headline means.
Finding the original price from a sale price
A question the three boxes don't answer directly: you paid $60 after a 25% discount — what was the original price? Divide by what remains after the discount: 60 ÷ (1 − 0.25) = 60 ÷ 0.75 = $80. The original price was $80. This works for any discount: paid price ÷ (1 − discount as a decimal).
Where percentages turn up in daily life
Shoppers meet them at every sale rail; diners meet them on every bill. Investors quote portfolio returns as percentages, teachers convert raw marks into percentages, and managers report month-over-month growth as percent change. Percentage points, meanwhile, belong to rates that are already percentages — mortgage rates, tax rates, election shares — where the distinction from relative change genuinely matters.
How to use
- Pick the question you want answered: X% of Y, X as a percent of Y, or percent change.
- Enter the numbers — decimals are fine (19% of 199.99 works).
- Press Calculate. Results are rounded to a sensible precision.
Limitations
- Percent change from an original value of zero is undefined — the calculator will tell you.
- "X is what percent of Y" needs a non-zero Y (division by zero is rejected).
- Results are rounded to 4 decimal places; for money, use the discount calculator which rounds to cents.
- Reverse percentages (finding the original from a discounted price) need a different formula — divide by (1 − discount), e.g. $60 ÷ 0.75 for a 25%-off price.
- Discounts stack sequentially, not additively: 20% then 10% off is a 28% total discount, not 30%.
Frequently asked questions
How do I calculate X percent of a number?
Multiply the number by X and divide by 100. For example, 19% of 199.99 is 199.99 × 19 ÷ 100 = 37.9981. The first box on this page does it for you.
How do I find what percent one number is of another?
Divide the part by the whole and multiply by 100. For example, 45 is (45 ÷ 180) × 100 = 25% of 180.
What is the difference between percent change and percentage points?
Percent change is relative: going from 50% to 60% is a 20% increase. Percentage points are the simple difference: that same move is a 10 percentage-point increase. They answer different questions.
How do I calculate a percent increase or decrease?
Subtract the original value from the new value, divide by the original value, and multiply by 100. A positive answer is an increase, a negative one a decrease.
Are my numbers uploaded anywhere?
No. The calculator runs 100% in your browser with JavaScript. Your numbers never leave your device, are never stored, and never sent to any server.
How do I calculate a 20% tip?
Multiply the bill by 20 and divide by 100. On a $48.50 bill that's a $9.70 tip and a $58.20 total. The first calculator box does it for you — enter 20 and 48.50.
How do I find the original price from a sale price?
Divide the price you paid by what remains after the discount. If you paid $60 after 25% off, the original price was 60 ÷ (1 − 0.25) = 60 ÷ 0.75 = $80.
How do I turn a test score into a percentage?
Divide the score by the total and multiply by 100. A score of 38 out of 50 is (38 ÷ 50) × 100 = 76%. Use the second calculator box for this.
Why do stacked discounts not add up?
Each discount applies to the already-reduced price. 20% then 10% off $100 leaves $72 — a 28% total discount, not 30%. For stacked discounts, use the discount calculator.