A board foot is a standard unit of measure referring to the volume of lumber in a 1 inch by 1 foot by 1 foot board. Assuming that the wood being measured is cut into 1-inch-thick boards, then 1 board foot converts to 1 square foot.
A board foot is a measure of volume, and wood may not always be 1 inch thick. For example, a 2-square-foot board that is 2 inches thick equals 4 board feet. To calculate the number of square feet a board will cover based on the board feet, the volume in board feet is divided by the thickness in inches.