Percentage Calculator
Percentages are everywhere — sale discounts, tips, grades, tax, pay rises — and the arithmetic trips everyone up sooner or later. This free percentage calculator answers the four questions people actually ask: what is X% of Y, X is what percent of Y, the percent increase or decrease between two numbers, and the percentage difference between them. Type and the answer appears instantly. Everything runs 100% in your browser — no sign-up, nothing uploaded.
100% client-side — nothing is uploaded or stored.
How to use it
Pick the tab that matches your question and type the numbers — the answer updates as you type, no button to press:
- X% of Y — shopping and tipping math. What is a 15% tip on a $64 bill? Type 15 and 64 → $9.60. What is 30% off $120? Type 30 and 120 → $36 off (so you pay $84).
- X is what % of Y — grades and shares. Got 42 out of 50 on a quiz? Type 42 and 50 → 84%. Spent $350 of a $2,000 budget? → 17.5%.
- % increase / decrease — growth and price changes. A stock moves from $40 to $50 → ▲ 25% increase. Your electricity bill drops from $140 to $112 → ▼ 20% decrease.
- % difference — comparing two values with no "before and after," like two products' prices or two cities' rents. Unlike percent change, the order of the numbers doesn't matter.
The Copy result button copies the answer as plain text so you can paste it into a spreadsheet, message, or document.
What it expects
Just numbers — whole numbers, decimals, and negatives all work (percent change from a loss-making quarter to a profitable one is a real use case). Leave a field empty and the calculator waits politely instead of guessing. A few edge cases are handled honestly rather than with a wrong answer: dividing by zero, or computing percent change from a starting value of zero, shows a short explanation instead of "Infinity" or "NaN."
One subtlety worth knowing: percent change treats the first number as the baseline, so direction matters — 50 to 100 is a +100% increase, but 100 to 50 is a −50% decrease, even though the gap is the same. If you want a direction-free comparison, use the percentage difference tab, which measures against the average of the two numbers instead.
The three percentage formulas
Every mode on this page is one of three formulas:
X% of Y = (X ÷ 100) × Y
X is what % of Y = (X ÷ Y) × 100
Percent change = ((new − old) ÷ old) × 100
Percentage difference uses a fourth: |A − B| ÷ ((A + B) ÷ 2) × 100 — the gap divided by the average, which is why swapping the two numbers can't change the answer.
Everyday examples
- Discounts: 25% off an $80 jacket — find 25% of 80 ($20 off), then subtract: you pay $60. Or find 75% of 80 directly: $60.
- Tips: 18% on a $52.50 dinner — 18% of 52.50 = $9.45. Round to $9.50 and nobody will object.
- Grades: 17 correct out of 20 questions — 17 is what % of 20? 85%.
- Pay rises: salary from $3,000 to $3,240 a month — a (3240 − 3000) ÷ 3000 × 100 = 8% increase.
- Tax: 5% sales tax on $240 — 5% of 240 = $12, total $252.
Frequently asked questions
- What is a percentage?
- A percentage is a way of expressing a number as a fraction of 100 — the word literally means "per hundred." So 25% is 25 out of every 100, or 25/100 = 0.25 as a decimal. That's why finding 25% of something is the same as multiplying it by 0.25.
- How do you find X% of Y?
- Multiply X by Y and divide by 100 — in other words, (X ÷ 100) × Y. What is 20% of 150? (20 ÷ 100) × 150 = 30. The first tab of this calculator does exactly that, instantly.
- How do you calculate percent increase or decrease?
- Subtract the old value from the new value, divide by the old value, and multiply by 100: ((new − old) ÷ old) × 100. A price rising from $40 to $50 is (50 − 40) ÷ 40 × 100 = a 25% increase. A positive answer means growth; a negative one means a drop.
- What is the difference between percent change and percentage difference?
- Percent change is directional — it measures growth or decline relative to the starting value, so order matters (50 to 100 is +100%, but 100 to 50 is −50%). Percentage difference is symmetric — it compares two values relative to their average, so the order doesn't matter: the difference between 50 and 100 is about 66.7% either way.
- How do you calculate a discount percentage?
- Use "X is what % of Y?" in reverse, or just multiply. A 25% discount on an $80 item means you pay 75% of the price: 80 × 0.75 = $60, saving $20. You can also find the saving first (25% of 80 = $20) and subtract it: 80 − 20 = $60.
- What is the difference between percent and percentage points?
- They measure different things. If a rate rises from 20% to 25%, that's an increase of 5 percentage points — but a 25% relative increase (5 ÷ 20 × 100). Mixing them up is one of the most common ways statistics mislead, so this calculator's percent-change mode always shows the relative change.
- Is my data uploaded anywhere?
- No. All calculations happen in your browser with JavaScript — the numbers you type never leave your device.