How to Calculate Percentage: Formula and Examples — Guide

Find a percent of a number

Convert the percent to a decimal by dividing by 100, then multiply by the number. For example, 15% of 80 is 0.15 × 80 = 12. For a discount, subtract that amount from the original price; the discount amount itself is not the final price. For tax, add the calculated tax when the quoted price excludes it. Check whether the displayed price already includes tax to avoid adding it twice.

Find what percent one value is

Divide the part by the whole and multiply by 100. If 18 of 60 questions are correct, 18 ÷ 60 × 100 = 30%. Confirm that the denominator is the full group you mean to compare against. A percentage is undefined when the whole is zero. When the group sizes differ, percentages can be more useful than raw counts, but include the sample size so readers understand how much data supports the comparison.

Calculate percentage change from the original

Subtract the original value from the new value, divide by the original, and multiply by 100. A change from 50 to 60 is (60 − 50) ÷ 50 × 100 = 20% increase. Reversing the comparison uses a different denominator: from 60 to 50 is a 16.7% decrease. State the baseline explicitly. Percentage points describe the difference between two percentages and should not be confused with percent change.

Worked example

15% of 80 = 0.15 × 80 = 12
18 out of 60 = 18 / 60 × 100 = 30%
Change from 50 to 60 = (60 − 50) / 50 × 100 = 20%

How do I calculate percentage increase?

Subtract the original from the new value, divide by the original value, and multiply by 100. Use the original as the baseline.

Reference and further reading

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