A room 10 feet long and 10 feet wide needs 100 square feet of carpeting to cover the floor. It is common to add an extra 20 percent in case of unforeseen problems, bringing the total to 120 square feet.
To determine the amount of any floor covering, the area of the room must be determined. For any rectangular or square room, the length and width of the room are measured separately. For example, a living room is 12 feet wide and 15 feet long. The next step is to multiple the length by the width, or 12 feet x 15 feet. This equals 180 square feet.