|Board Foot Measure|
|SI base units||?0.002359737 m3|
|US Customary||1⁄12 ft3|
The board foot or board-foot is a unit of measurement for the volume of lumber in the United States and Canada. It equals the volume of a one-foot (305 mm) length of a board, one foot wide and one inch (25.4 mm) thick.
Board foot can be abbreviated as FBM (for "foot, board measure"), BDFT, or BF. A thousand board feet can be abbreviated as MFBM, MBFT, or MBF. Similarly, a million board feet can be abbreviated as MMFBM, MMBFT, or MMBF.
One board foot equals:
The board foot is used to measure rough lumber (before drying and planing with no adjustments) or planed/surfaced lumber. An example of planed lumber is softwood 2 × 4 lumber sold by large lumber retailers. The 2 × 4 is actually only 1+1⁄2 in × 3+1⁄2 in (38 mm × 89 mm), but the dimensions for the lumber when purchased wholesale could still be represented as full 2 × 4 lumber, although the "standard" can vary between vendors. This means that nominal lumber includes air space around the physical board when calculating board feet in some situations, while the true measurement of "board feet" should be limited to the actual dimensions of the board.
See dimensional lumber for a full discussion of the relationship of actual and nominal dimensions. Briefly, for softwoods, to convert nominal to actual, subtract 1⁄4 inch (6 mm) for dimensions under 2?; subtract 1⁄2 inch (13 mm) for dimensions over 2? and under 8?; and subtract 3⁄4 inch (19 mm) for larger measurements. The system is more complicated for hardwoods.