Free online percentage calculator — find percentage of a number, calculate what percent one number is of another, compute percentage change, figure out discounts, and split tips. Five calculators in one, all running locally in your browser. No signup, no ads popups, just results.
5-in-1 · Instant ResultsHow to Calculate Percentages
What Is a Percentage?
A percentage represents a fraction of 100. The word comes from Latin "per centum" meaning "by the hundred." 1% = 1/100 = 0.01. Percentages are everywhere — from sale discounts and restaurant tips to stock market changes, test scores, and tax rates.
The Four Core Percentage Calculations
| What You Want | Formula | Example |
|---|---|---|
| X% of a number | Number × X ÷ 100 | 15% of 200 = 30 |
| What % is A of B? | (A ÷ B) × 100 | 30 is 15% of 200 |
| % change from A to B | (B − A) ÷ |A| × 100 | 100 → 120 = +20% |
| Discount price | Price × (1 − Discount% ÷ 100) | $200 at 20% off = $160 |
Common Percentage Conversions
| Percent | Decimal | Fraction | Real-World Use |
|---|---|---|---|
| 1% | 0.01 | 1/100 | Cashback rates |
| 5% | 0.05 | 1/20 | Sales tax (some states) |
| 10% | 0.1 | 1/10 | Basic tip, 10% off sale |
| 15% | 0.15 | 3/20 | Standard tip (pre-tax) |
| 18% | 0.18 | 9/50 | Standard restaurant tip |
| 20% | 0.2 | 1/5 | Good service tip, 20% off |
| 25% | 0.25 | 1/4 | Quarter, 25% off sale |
| 33.33% | 0.3333 | 1/3 | One-third split |
| 50% | 0.5 | 1/2 | Half-price sale |
| 100% | 1.0 | 1/1 | The whole thing |
Frequently Asked Questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. For example, to find 15% of 200: 200 × 15 ÷ 100 = 30. You can also think of it as 200 × 0.15. Our calculator handles this in real-time — just type and the answer appears.
How do I work out what percentage one number is of another?
Divide the smaller (part) by the larger (whole) and multiply by 100. For example: 45 out of 300 as a percentage = (45 ÷ 300) × 100 = 15%. This is perfect for test scores, budget tracking, and data analysis.
How is percentage increase or decrease calculated?
Use the formula: (new − old) ÷ |old| × 100. Positive = increase, negative = decrease. Example: your salary goes from $50,000 to $55,000 — that's a 10% raise. If your portfolio drops from $10,000 to $8,500, that's a 15% loss.
How does the tip calculator work?
Enter your bill total, choose a tip percentage (15-20% is standard in the US), and optionally the number of people splitting the bill. You'll see the tip amount, total with tip, and per-person share. Default suggestion is 18% — the most common US restaurant tip rate.
Is this calculator accurate?
Completely. Every calculation uses standard IEEE 754 floating-point arithmetic with appropriate rounding. Everything runs in your browser — no data is sent anywhere. You can even use it offline once the page loads.