Calculating a percentage of an amount
Finding a percentage of an amount is a skill you'll use in loads of real-life situations—like working out how much discount you’re getting in a sale, calculating tips at a restaurant, or figuring out how much battery life you’ve got left. It’s all about taking a chunk of something and seeing what part of the whole it represents. Jump to the questions
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Topic guide
What this worksheet practises
This worksheet practises calculating a percentage of a given amount without using a calculator.
Key method
To find a percentage of an amount without a calculator, build up the required percentage using simple building blocks like 10%, 5%, and 1%.
- To find 10%, divide the amount by 10.
- To find 5%, find 10% and halve it.
- To find 1%, divide the amount by 100.
Once you have these building blocks, you can add or multiply them to find any other percentage.
Worked example
Calculate 15% of £80.
Step 1: Find 10%.
£80 ÷ 10 = £8
Step 2: Find 5%.
Halve the 10% value: £8 ÷ 2 = £4
Step 3: Add the 10% and 5% values together to make 15%.
£8 + £4 = £12
Therefore, 15% of £80 is £12.
Useful tips
If you need to find a multiple of 10%, such as 30%, simply find 10% and multiply your answer by 3. You can use similar logic for numbers ending in 5 or 1, assembling the pieces until you reach the target percentage.
How to check your answer
You can verify your logic by checking if the answer feels proportional. If you are asked for 45%, your answer should be slightly less than half of the original amount. If it is larger, you know a mistake has been made in the calculation.