How Do You Add Percentages?

By Staff WriterLast Updated Mar 29, 2020 8:31:36 PM ET

To add a percentage to a given number involves multiplying the base number by a decimal that represents the percentage fraction. Adding two percentages together involves the opposite, or converting the percentages to fractions.

To calculate the addition or subtraction of percentages, it is first necessary to understand the relationship between a percentage and its decimal representation.

To Add a Percentage to a Given Number

Multiply the base number by 1 plus the percentage as a decimal. For example, to add 25 percent to the number 4: 4 x (1 + 0.25) = 4 x 1.25 = 5.

To Add Two Percentages Together

Convert the percentages to fractions with a common denominator and perform the simple addition operation. Then the answer may be converted back to a percentage. For example, to add 20 percent to 30 percent: 20 / 100 + 30 / 100 = 50 / 100 or 50 percent.