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How to Find a Percentage

In one line: A percentage means 'out of 100', so to find what percentage one number is of another, divide the part by the whole and multiply by 100.

Why it works

Percentages are everywhere: shop discounts, battery levels, quiz scores and the chance of rain. They let you compare things of different sizes fairly. For example, is 18 out of 24 better than 20 out of 25? It is hard to tell until you turn both into percentages: 75% and 80%. Now it is easy to see that 20 out of 25 is better.

Think of it like: Imagine two pizzas cut into different numbers of slices, one into 24 and one into 25. Comparing slices is confusing. Finding a percentage is like re-cutting every pizza into exactly 100 equal slices, so you can compare how many slices each person ate on the same scale. (Where this breaks: Real pizzas can't be more than whole, but percentages can go above 100%. If something doubles, it is 200% of what it was. Percentages also don't have to be whole numbers, such as 12.5%.)

Worked example

Sam got 18 out of 24 questions right on a spelling quiz. What percentage did Sam get right?

  1. Find the part and the whole. The part is what Sam got right (18). The whole is the total number of questions (24).
  2. Write it as a fraction with the part on top: 18/24.
  3. Divide the part by the whole: 18 ÷ 24 = 0.75.
  4. Multiply by 100 to change it to 'out of 100': 0.75 × 100 = 75.
  5. Add the percent sign (%) and check: 75% is three quarters, and 24 ÷ 4 × 3 = 18, so the answer makes sense.

Answer: Sam got 75% of the questions right.

Common mistakes

  • Dividing the whole by the part (24 ÷ 18) gives an answer over 100%, so always put the part on top and divide it by the whole.
  • Stopping at the decimal and writing 0.75% instead of 75%, so remember to multiply by 100 before adding the % sign.
  • Thinking 20% of a number means dividing by 20, so remember that 20% means 20 out of 100, which is 0.2, and multiply instead (20% of 50 = 50 × 0.2 = 10).
  • Using the new amount as the whole when finding a percentage increase or decrease, so always divide the change by the starting amount.

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What percentage is 7 out of 10?

Questions parents ask

What year do kids learn how to find percentages?

In Australia and the UK, children usually meet percentages in Year 5 and work out percentages of amounts by Year 6. In the US, percentages are a big focus in Grade 6. Percentage increase and decrease usually follow in Years 7–8 (Australia and UK) or Grade 7 (US).

How can I help my child with percentages at home?

Use real life: ask your child to work out a sale discount while shopping, or what percentage of a game level they have finished. Start with easy benchmarks like 50% (half), 25% (a quarter) and 10% (divide by 10), then build up to harder ones.

Should my child use a calculator to find percentages?

A calculator is useful for awkward numbers, but children should first learn to do simple ones in their head. Knowing that 10% means dividing by 10 lets them quickly find 5%, 20% or 30%, and helps them spot calculator answers that don't make sense.

What is the difference between 'percent' and 'percentage'?

'Percent' is used with a number and means 'out of 100', as in '40 percent' or 40%. 'Percentage' is the general word for the amount, as in 'What percentage did you get?' They describe the same idea.