Your roofing surface is often measured in "squares". When someone refers to a "square" it is equal to 100 square feet of your roof. Therefore to figure out how many squares your roof is you would take the total square feet measurement of your roof and then divide that by 100. For example, if your roof is 15,000 square feet in total you would divide that by 100 in order to determine that your roof is 150 squares. (15,000/100 = 150 Squares)