Percentage of Number
Calculate what X% of a number is.
What does "percentage of" mean?
"Per cent" means "per hundred" — a fraction with a denominator of 100. When you calculate X% of a number, you find what fraction X/100 of that value is. This is one of the most fundamental calculations in everyday numeracy, applied in tipping, tax, discounts, statistics, and financial analysis. The formula requires just one multiplication after converting the percentage to a decimal.
Result = (Percentage ÷ 100) × Number
Examples:
15% of 200 = 0.15 × 200 = 30
8.5% of 1,400 = 0.085 × 1,400 = 119
110% of 50 = 1.10 × 50 = 55 (more than the whole)
0.5% of 10,000 = 0.005 × 10,000 = 50The three percentage problem types
All percentage problems are variations of Part = Percentage × Whole. The unknown variable determines which type you have:
| Question type | Example | Formula | Answer |
|---|---|---|---|
| What is X% of N? | What is 20% of 150? | Part = % × Whole / 100 | 30 |
| X is what % of N? | 30 is what % of 150? | % = Part ÷ Whole × 100 | 20% |
| X% of what = N? | 20% of what = 30? | Whole = Part ÷ (% / 100) | 150 |
Quick mental maths shortcuts
Everyday applications
- Restaurant tips: A 15% tip on a €68 bill — 10% = €6.80, 5% = €3.40, total = €10.20.
- Sales tax and VAT: 21% VAT on a €200 product adds €42, giving a total of €242.
- Discounts: A 30% discount on a €450 item saves €135, leaving a price of €315.
- Investment returns: A 7% annual return on a €10,000 portfolio earns €700 in year one.
- Exam scores: Scoring 72% on a 50-question test means getting 36 questions right (0.72 × 50 = 36).
Frequently asked questions
How do I calculate X percent of a number?
Multiply the number by the percentage divided by 100. For example, 20% of 150 is 150 × 0.20 = 30.
How do I work out a tip or discount with this?
Enter the percentage and the amount. For a 15% tip on 80, you get 12; for 30% off 80, calculate 30% (24) and subtract it to get 56.
What is the difference between "percent of" and "percent change"?
"Percent of" finds a portion of a single number, while percent change compares two numbers to measure increase or decrease. Use the percentage change tool for the latter.
How do I reverse the calculation?
To find what percentage one number is of another, divide the part by the whole and multiply by 100. For example, 30 is (30 ÷ 150) × 100 = 20% of 150.
Calculates what a specific percentage of a number is. This is the most fundamental percentage calculation: "What is X% of Y?"
Result = (Percentage ÷ 100) × Number