How to Find a Percentage of a Number (Easy Methods)
By the TimesTable.co team · Updated · 4 min read
"Per cent" means "out of 100", so 30% of something is 30 out of every 100. Children meet percentages in sales, battery icons and test scores, but working them out can feel mysterious. The good news is that you only ever need a few building blocks: 10%, 5%, 1% and the easy fractions. Everything else is made from those.
What does a percentage mean?
A percentage is a fraction out of 100. 25% means 25/100, which is the same as 1/4. Picture a hundred grid: 25% is 25 of the 100 squares shaded. The fractions, decimals and percentages explorer lets children shade a hundred grid and see the fraction, decimal and percentage change together. For more on how the three connect, see fractions, decimals and percentages.
How does the 10% method work?
Work out these building blocks first, then add or subtract them:
| Percentage | How to find it | Of 360 |
|---|---|---|
| 100% | The whole number | 360 |
| 50% | Halve it | 180 |
| 10% | Divide by 10 | 36 |
| 5% | Halve 10% | 18 |
| 1% | Divide by 100 | 3.6 |
Dividing by 10 moves every digit one place to the right, so 10% of 360 is 36 and 10% of 45 is 4.5. That's why children need to be confident with place value before percentages.
What do worked examples look like?
- 15% of 360: 10% = 36, 5% = 18. 36 + 18 = 54.
- 30% of 250: 10% = 25, so 30% = 3 × 25 = 75.
- 35% of 80: 10% = 8, so 30% = 24. 5% = 4. 24 + 4 = 28.
- 90% of 70: 10% = 7. 100% − 10% = 70 − 7 = 63.
- 23% of 400: 10% = 40, so 20% = 80. 1% = 4, so 3% = 12. 80 + 12 = 92.
Notice how often the times tables appear: 3 × 25, 3 × 4. Solid times tables make percentages far quicker, because most of the work is multiplying a small building block. If they're not there yet, start with how to learn times tables.
Which percentages are easier as fractions?
Some percentages are faster to find as a fraction of the number:
| Percentage | Fraction | Method | Example: of 60 |
|---|---|---|---|
| 50% | 1/2 | Divide by 2 | 30 |
| 25% | 1/4 | Divide by 4 | 15 |
| 75% | 3/4 | Divide by 4, times by 3 | 45 |
| 20% | 1/5 | Divide by 5 | 12 |
| 33⅓% | 1/3 | Divide by 3 | 20 |
Is there a shortcut for awkward percentages?
Yes: percentages can be swapped round. 8% of 50 is the same as 50% of 8, which is 4. It works because both are 8 × 50 ÷ 100. So if a question looks hard, try it the other way. 4% of 25? That's 25% of 4, which is 1. It's the same idea as 3 × 7 being the same as 7 × 3.
How do you find what percentage one number is of another?
Write it as a fraction, then make the denominator 100. "What percentage is 12 of 40?" is 12/40. Multiply the top and bottom by 2.5 to get 30/100, so it's 30%. Or simplify first: 12/40 = 3/10 = 30/100. For test scores, 18 out of 20 is 18/20 = 90/100 = 90%. This uses equivalent fractions.
How do you do it on a calculator?
Turn the percentage into a decimal by dividing by 100, then multiply: 35% of 80 is 0.35 × 80 = 28. It's still worth estimating first. "35% is a bit more than a third, and a third of 80 is about 27", so 28 looks right.
What mistakes do children commonly make?
- Dividing by the percentage: finding 20% of 60 by working out 60 ÷ 20 = 3. It's 60 ÷ 5 = 12.
- Finding 5% by dividing by 5: that gives 20%. 5% is half of 10%, so divide by 10 and then halve.
- Place value slips: 10% of 45 given as 45 or 0.45 instead of 4.5.
- Adding percentages to the number: "a 10% discount on £40" means taking away £4, not finding £4.
How can you practise at home?
- Work out real discounts when shopping: "20% off £15, how much do we save?"
- Turn test or game scores into percentages.
- Explore the hundred grid on the percentages page.
- Practise the division that sits underneath, like dividing by 4 or 5, with step-by-step division.
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Frequently asked questions
How do you find 10% of a number?
Divide it by 10. 10% of 360 is 36, and 10% of 45 is 4.5.
How do you work out 15% of a number?
Find 10%, halve it to get 5%, then add the two. For 15% of 360: 10% is 36, 5% is 18, so 15% is 54.
How do you find 1% of a number?
Divide it by 100. 1% of 400 is 4, so 3% of 400 is 12.
What is the easiest way to find 25% or 50%?
Use fractions. 50% is a half, so divide by 2. 25% is a quarter, so divide by 4 (or halve twice). 75% is three quarters.
How do you work out a percentage on a calculator?
Change the percentage to a decimal by dividing by 100, then multiply. For 35% of 80, type 0.35 × 80 = 28.
When do children learn percentages?
In England, Year 5 introduces the % sign and percentage equivalents of simple fractions, and Year 6 finds percentages of amounts, such as 15% of 360. In the US, finding a percent of a quantity is a Grade 6 standard (6.RP.A.3c).