Put simply, the price of carpet is usually expressed in square yards. As a quick refresher in math, remember a yard is 3 feet so a square yard equals 3 feet by 3 feet or 9 square feet. The width of the carpet: Carpet is usually manufactured in 12-foot widths. If all rooms were 12 feet wide there would be little problem. But let's say your room is 10 feet by 10 feet. That's 100 square feet. If you bought 100 square feet, you would have to do a lot of cutting and seam work to cover this room. Here's why: If the carpet is 12 feet wide, 100 square feet would mean the length would be 8 feet, 4 inches (100 divided by 12 = 8.4.