How to find a percentage of any number

Start with the whole

“Of” tells you which number is the base. In 18% of 240, 240 is the whole and 18% is the share. Divide the percent by 100 to write it as a decimal: 18% becomes 0.18. Then multiply the base by that decimal. OpenStax explains the percent equation.

Do a scale check before trusting the result. Since 18% is less than one fifth, the answer should be a little below 48. If you get 4,320, you likely multiplied by 18 rather than 0.18.

When the base is unclear

“18% of what?” and “240 is 18% of what?” are different questions. For the second, divide 240 by 0.18 to recover the whole. Write down what is the part and what is the whole before calculating.

Three ways to recognise the same question

“18 percent of 240”, “0.18 times 240”, and “18 out of every 100 parts of 240” express the same operation. You can choose the form that makes the calculation easiest. For 10%, divide by ten; for 5%, take half of 10%; for 15%, add those two pieces. That mental method can check a calculator result without repeating exactly the same keystrokes.

If the whole represents money, carry the currency symbol through the calculation. If it represents people, a fractional answer may need a real-world interpretation rather than automatic rounding. A percentage can be above 100%, in which case the part is larger than the reference whole.

A useful second example

For 7.5% of £80, first find 10% (£8) and 2.5% (£2), then subtract to get £6. The direct calculation, £80 × 0.075, agrees. If someone asks “£6 is what percent of £80?”, reverse the roles: £6 ÷ £80 × 100 = 7.5%. Reading the wording carefully is usually more important than choosing a fast multiplication trick.

Try it with your numbers

Try “What is 18% of 240?” and then change only the percentage or the base to compare outcomes. If the amount is money, include its currency in the question so the answer keeps that context. The tool can show multiplication steps, but you should still check what “of” refers to when several amounts appear in the same sentence.