Maths · Intermediate

How to find a percentage of an amount (without a calculator)

‘Per cent’ means ‘out of 100’. Finding 15% of £240 means finding 15 hundredths of it. Without a calculator, the quickest way is to build the percentage from easy pieces like 10%, 5% and 1%.

Ages
9+ (rough guide)
Level
Intermediate
Subject
Maths
Time
15–25 minutes
Format
Online + printable
Stage
UK Year 6 onwards · roughly US Grade 6
Try it online Print worksheet & answers Online + Print
  1. 1Learn it
  2. 2See it worked
  3. 3Try it online
  4. 4Print it
  5. 5Check your answer

Before you start

Who it's for and what to know first

Dividing by 10 and 100, and adding decimals.

Learn it

How it works

  • 50% is half. 25% is a quarter. 10% is ÷ 10. 1% is ÷ 100.
  • Build other percentages from these. 5% is half of 10%. 15% = 10% + 5%. 30% = 3 × 10%.
  • 75% = 50% + 25%, or three quarters.
  • To increase by a percentage, find the percentage and add it on. To decrease, subtract it.
  • Calculator method: change the percentage to a decimal (15% = 0.15) and multiply.

Worked example 1

15% of £240

  1. 10% of 240 = 24.
  2. 5% is half of that = 12.
  3. 24 + 12 = 36.

Answer: £36

Worked example 2

Increase £40 by 20%

  1. 10% of 40 = 4, so 20% = 8.
  2. 40 + 8 = 48.

Answer: £48

Try it online · print it · check it

Practice questions

Type numbers only. You do not need to type £. Type your answer, then press Check answers.

Tips

Common mistakes

  • Dividing by the percentage: 15% of 240 is not 240 ÷ 15.
  • Finding the percentage but forgetting to add it on for an increase.
  • Mixing up 5% (half of 10%) with 50%.

Where next?

EasierFractions of amountsFinding a fraction of an amount means working out, for example, 3/4 of 20 sweets or 2/5 of £45.RelatedComparing prices and unit pricingThe cheapest price is not always the best value.RelatedSimple and compound interestInterest is money paid for using money.MoreAll Maths resourcesMaths resources that teach the method before the practice.

Last reviewed: 25 September 2026