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Calculating percentages

The guidance below will help you work through percentage calculation problems including those found on the percentage worksheets page. As you guide your child you should also take the opportunity to explain the importance and relevance of percentage calculations: pay rises, allowance rises, interest rates, discounts on sale items etc. Learning is always improved when the relevance of what is being learned is appreciated.

What is a percentage?

Percent means “for every 100” or "out of 100." The (%) symbol as a quick way to write a fraction with a denominator of 100. As an example, instead of saying "it rained 14 days out of every 100," we say "it rained 14% of the time."

Percentages can be written as decimals by moving the decimal point two places to the left:

Decimals can be written as a percentages by moving the decimal point two places to the right:

Formula for calculating percentages

The formula for calculating percentages or for converting from percentages are relatively simple.

To convert a fraction or decimal to a percentage, multiply by 100:

To convert a percentage to a fraction, divide by 100 and reduce the fraction (if possible):

Examples of percentage calculations

The following two examples show how to calculate percentages.

1) 12 people out of a total of 25 were female. What percentage were female?

2) The price of a $1:50 candy bar was to be increased by 20%. What was the new price?

This Percentage Chart shows what 15% of $1 through $100 is.

Tip: When calculating a percentage of a number, first calculate what 1% is (by dividing by 100) and then multiply the 1% by whatever % is required.
e.g What is 30% of 2.5? 1% is .025 and 30% is .025 x 30 = .75