How to Subtract Percentages

By Molly MaGuire
Typically, sale prices are shown in percentages.

There are a couple of methods you can use to subtract percentages. You can calculate the percentage value and then subtract it from the total, or you may subtract the percentage from 100 to determine the remaining percentage and then calculate the percentage value. To complete either method, remember that the term “percent” means “per 100.” So, 10 percent means 10 per 100 or 10/100; 25 percent means 25 per 100 or 25/100 and so on.

Calculate, Then Subtract

Your store announces a 20-percent off sale on its cereal brands. In this example, assume that the regular price of the cereal you want to purchase is $4.50.

To determine how much the cereal will cost at 20 percent off, follow these steps:

Change the percentage off to a decimal: 20 percent = 20/100 = 0.20.

Multiply the regular price by the percentage off decimal to determine the percentage value: 4.50 x 0.20 = 0.90.

Subtract the percentage value from the regular price: 4.50 – 0.90 = 3.60.

The sale price of the cereal is $3.60.

Subtract, Then Calculate

Milk is on sale at the grocery store for 10 percent off. The regular price for milk is $3.50. To determine what you will pay using the subtract-then-calculate method, follow these steps:

Subtract the percent off from 100 to find the remaining percentage: 100 percent minus 10 percent = 90 percent.

Change the remaining percentage to a decimal: 0.90.

Multiply the regular price by the remaining percentage decimal: 3.50 x 0.90 = 3.15.

The sale price of the milk is $3.15.

About the Author

Molly MaGuire has a Bachelor of Science in computer science and a Master of Science in international relations. She has taught at the university level for more than seven years and has worked as an instructional designer for more than nine years. She enjoys researching and discussing topics such as education, politics and technology.