Questions such as “18 is what percent of 24?” all use the same relationship. The only tricky part is deciding which number is the part and which is the whole.
Use part divided by whole
Write the amount you are measuring first, then divide it by the total amount. Multiply the result by 100. For 18 out of 24, 18 ÷ 24 is 0.75, and 0.75 × 100 is 75%.
Identify the whole correctly
The whole is the complete reference amount. If 14 people out of a group of 20 chose tea, 14 is the part and 20 is the whole. Reversing them produces 142.86%, which answers a different question.
Work with money and targets
If you saved $120 toward a $600 target, your progress is 120 ÷ 600 × 100 = 20%. If $36 of a $240 bill is tax and fees, those charges represent 15% of the bill.
Handle results above 100%
A result above 100% is valid when the part is larger than the reference whole. If actual sales are 130 against a target of 100, achievement is 130%. State the reference clearly so the result is not misleading.
A calculator is often the quickest way to check your mental math. The important part is using the right starting value.
Open a calculator →Common questions
Which number goes on the bottom?
Use the whole, total, target, or reference amount as the denominator.
What percentage is 25 of 200?
25 ÷ 200 × 100 = 12.5%.
Why did I get more than 100%?
The measured part may be larger than the reference amount, or the part and whole may have been reversed.
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