The board-foot is a specialized unit of measure for the volume of lumber in the United States and Canada. It is the volume of a one-foot length of a board one foot wide and one inch thick.
Board-foot can be abbreviated FBM (for "foot, board measure"), BDFT, or BF. Thousand board-feet can be abbreviated as MFBM, MBFT or MBF.
In Australia and New Zealand the term super foot or superficial foot was used to mean the same.[1][2][3]
One board-foot equals:
Board foot is the unit of measure for rough lumber (before drying and planing with no adjustments) or planed/surfaced lumber. An example of planed lumber is softwood 2x4 lumber one would buy at a large lumber retailer. The 2x4 is actually only 11⁄2 × 31⁄2 in (38 × 89 mm) but the board footage for the lumber when purchased wholesale could still be represented as full 2x4 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.
For planed lumber, board-feet refer to the nominal thickness and width of lumber, calculated in principle on its size before drying and planing. Actual length is used.
See dimensional lumber for a full discussion of the relationship of actual and nominal dimensions. Briefly, for softwoods, to convert nominal to actual, subtract ¼ inch for dimensions under 2 inches (51 mm); subtract ½ inch for dimensions under 8 inches (203 mm); and subtract ¾ inch for larger measurements. The system is more complicated for hardwoods.
An Essex table is a tabulation of the number of board feet in lumber of varying dimensions.[4]