Board foot

The board foot is a specialized unit of volume for measuring lumber in the United States. It is the amount of wood in a 12-inch long 1-inch-by-12-inch board, or the equivalent. Unfortunately, it is not truly a measure of volume, due to nominal and actual measures used in the lumber busines. In addition, the definition is different for hardwood and softwood.

To be exact, for hardwood, the board footage is defined as BF = SM × T, where T is the nominal thickness in inches and SM = L × W / 12, where L is nominal length in feet, truncated (rounded down) to the nearest foot, W is actual width in inches, and SM is rounded to the nearest whole number.

For softwood, BF = L × W × T / 12, where L is nominal length in feet, truncated to the nearest even foot, W is nominal length in inches, T is nominal thickness in inches, and the result is rounded to the nearest hundredth of a board foot.