Consider this; a yard is 36 inches, a square yard is 36 in. X 36 in. or 1296 sq. inches. A twelve-foot wide carpet is 12 ft (width) times twelve inches (inches in a foot) or 144 inches across. 1296 sq inches (a square yard) divided by the carpet width in inches (144) equals 9. So 9-inches of roll length times the 12-ft carpet width is a square yard. 12 inches of roll length divided by 9 inches (sq yard) equals 1.33. Carpet roll length (in linear feet) times 1.33 will give you square yards.