Percentage Calculator
Three calculators in one: find what X% of a number is, determine what percentage one number is of another, and compute percentage change between two values. Instant, free, in your browser.
1 What is X% of Y?
Use this to calculate tips, discounts, tax, commission, and more.
2 X is what % of Y?
Use this to calculate grades, completion rates, or market share.
3 % Change from X to Y
Find the percentage increase or decrease between two values.
Common Percentages Reference Table
Quick lookup: X% of common amounts. All values rounded to 2 decimal places.
| Amount | 5% | 10% | 15% | 20% | 25% | 50% |
|---|---|---|---|---|---|---|
| 50 | 2.50 | 5 | 7.50 | 10 | 12.50 | 25 |
| 100 | 5 | 10 | 15 | 20 | 25 | 50 |
| 200 | 10 | 20 | 30 | 40 | 50 | 100 |
| 500 | 25 | 50 | 75 | 100 | 125 | 250 |
| 1,000 | 50 | 100 | 150 | 200 | 250 | 500 |
| 5,000 | 250 | 500 | 750 | 1000 | 1250 | 2500 |
How to Calculate Percentages
A percentage is a number expressed as a fraction of 100. The word comes from the Latin per centum, meaning "by the hundred." Percentages are used everywhere: grades, discounts, tax rates, interest rates, poll results, nutrition labels, and statistics.
Formula 1 — Find X% of Y
Result = (X ÷ 100) × Y Example: 15% of 200
= (15 ÷ 100) × 200 = 0.15 × 200 = 30
Formula 2 — X is what % of Y?
Percentage = (X ÷ Y) × 100 Example: 30 is what % of 200?
= (30 ÷ 200) × 100 = 0.15 × 100 = 15%
Formula 3 — % Change
Change = ((New − Old) ÷ |Old|) × 100 Example: Change from 80 to 100
= ((100 − 80) ÷ 80) × 100 = 20/80 × 100 = +25%
Real-world uses
| Use case | Formula used | Example |
|---|---|---|
| Restaurant tip | X% of bill amount | 15% of $45 = $6.75 |
| Sale discount | Subtract X% of original price | 20% off $120 → $120 − $24 = $96 |
| Tax on purchase | X% of purchase price | 8% tax on $250 = $20 tax → $270 total |
| Exam score | Score ÷ max × 100 | 42 out of 50 = 84% |
| Salary raise | % change from old to new salary | $50,000 → $55,000 = +10% raise |
| Investment return | % change from cost to current value | Bought at $100, now $135 = +35% |
Frequently Asked Questions
How do I calculate 20% of a number?
Multiply the number by 0.20 (or divide by 100 then multiply by 20). For example, 20% of 350 = 350 × 0.20 = 70. The general formula is: Result = (Percentage ÷ 100) × Number. So 20% of 350 = (20 ÷ 100) × 350 = 70. This is useful for calculating tips, discounts, taxes, and commissions.
How do I find what percentage one number is of another?
Divide the part by the whole and multiply by 100. For example, if you scored 45 out of 60 on a test: (45 ÷ 60) × 100 = 75%. The general formula is: Percentage = (Value ÷ Total) × 100. This is used for calculating grades, market share, completion rates, and survey responses.
What is percentage change vs percentage point change?
These are different things that are often confused. A percentage change measures the relative change: if something goes from 40% to 50%, the percentage change is ((50 − 40) ÷ 40) × 100 = 25%. A percentage point change is simply the arithmetic difference: 50% − 40% = 10 percentage points. In reporting, "the approval rating rose 10 percentage points (from 40% to 50%)" is precise; saying "rose 10%" is ambiguous and often incorrect.
How do I calculate a tip at a restaurant?
Use the "What is X% of Y?" calculator. Enter the tip percentage (typically 15%, 18%, or 20%) and the bill total. For a $65 bill: 15% tip = $9.75, 18% tip = $11.70, 20% tip = $13.00. A quick mental shortcut: find 10% by moving the decimal point one place left ($65 → $6.50), then adjust. For 20%, double the 10% figure ($6.50 × 2 = $13.00). For 15%, take 10% and add half of it ($6.50 + $3.25 = $9.75).
What is 1% of 1 million?
1% of 1,000,000 = (1 ÷ 100) × 1,000,000 = 10,000. More generally, 1% of any number equals that number divided by 100. So 1% of $1 million = $10,000; 1% of $1 billion = $10 million; 1% of the world population (~8 billion) ≈ 80 million people. This makes 1% a useful mental benchmark — when a company says "we only take a 1% fee" on a large transaction, that can still be a significant dollar amount.
How do you reverse a percentage? (If the final price is $85 after 15% off, what was the original?)
To reverse a percentage discount, divide the final price by (1 − discount rate). If $85 is the price after a 15% discount: Original = $85 ÷ (1 − 0.15) = $85 ÷ 0.85 = $100. The mistake many people make is adding 15% back on: $85 × 1.15 = $97.75, which is wrong because the 15% was applied to the original $100, not to $85. Similarly, to reverse a percentage increase: if a price rose 20% to $120, the original was $120 ÷ 1.20 = $100.