Calculators
How to Find a Percentage of a Number
Tips at a restaurant. VAT on an invoice. Discount off a price. Marks on a test. All four use the same one-line formula. Here's the method, the formula, and shortcuts for common percentages you can do in your head.
The formula
Result = (Percentage ÷ 100) × Number
or equivalently: Number × (Percentage / 100)
That's it. Divide the percentage by 100 to convert it to a decimal, then multiply. The order of multiplication doesn't matter — both give the same result.
Step-by-step examples
15% tip on a £64 restaurant bill
- Convert: 15 ÷ 100 = 0.15
- Multiply: 0.15 × 64 = £9.60
- Tip = £9.60
20% VAT on a £250 item
- Convert: 20 ÷ 100 = 0.20
- Multiply: 0.20 × 250 = £50
- VAT = £50 → Total = £300
35% off a £180 jacket
- Convert: 35 ÷ 100 = 0.35
- Discount: 0.35 × 180 = £63
- Sale price: £180 − £63 = £117
Exam score: 54 out of 75
- Divide part by whole: 54 ÷ 75 = 0.72
- Multiply by 100: 0.72 × 100 = 72%
- Score = 72%
Mental math shortcuts
You don't always need a calculator. These shortcuts work for common percentages and get you to an exact or very close answer in seconds.
For non-standard percentages, combine: 15% = 10% + 5%. 35% = 25% + 10%. 45% = 50% − 5%. These get you exact answers, not estimates.
Just need the number fast?
Type the percentage and the number. Result is instant, formula shown.
Use the calculator →Frequently asked questions
How do you find a percentage of a number?
Divide the percentage by 100 and multiply by the number. To find 25% of 80: (25 ÷ 100) × 80 = 0.25 × 80 = 20. This works for any percentage — fractional ones included. 12.5% of 160 is (12.5 ÷ 100) × 160 = 0.125 × 160 = 20.
What is 20% of 100?
20% of 100 is 20. In general, finding a percentage of 100 is the simplest case — the answer is just the percentage number. 35% of 100 = 35. 7.5% of 100 = 7.5. For other numbers, divide the percentage by 100 and multiply by the number.
How do I calculate a 15% tip?
Find 10% of the bill by moving the decimal one place left, then add half of that for 5%, giving you 15%. On a £48 bill: 10% = £4.80. 5% = £2.40. Total 15% tip = £4.80 + £2.40 = £7.20. Or just multiply £48 × 0.15 = £7.20. Most people use the mental math shortcut for quick estimates.
How do you calculate VAT at 20%?
Multiply the pre-tax price by 0.20 to get the VAT amount, or multiply by 1.20 to get the total including VAT. On a £150 item: VAT = £150 × 0.20 = £30. Total = £150 × 1.20 = £180. To find the pre-tax price from a VAT-inclusive price, divide by 1.20 — a £180 VAT-inclusive price has a pre-tax value of £180 ÷ 1.20 = £150.
How do I calculate a discount percentage?
Multiply the original price by the discount rate as a decimal. A 30% off discount on £120: £120 × 0.30 = £36 off, so the sale price is £120 − £36 = £84. Or compute the sale price directly: £120 × (1 − 0.30) = £120 × 0.70 = £84. The multiplier method (×0.70) is one step instead of two.
What are some quick mental shortcuts for common percentages?
10%: move the decimal one place left (10% of 340 = 34). 5%: halve the 10% figure (5% of 340 = 17). 1%: move the decimal two places left (1% of 340 = 3.4). 20%: double the 10% figure (20% of 340 = 68). 25%: divide by 4 (25% of 340 = 85). 50%: divide by 2 (50% of 340 = 170). Combine these for non-standard percentages: 15% = 10% + 5%.