Board-Foot Measure
Unit of... Volume
Symbol: FBM
Unit conversions
1 FBM in... is equal to...
   SI base units    ≈0.002359737 m3
   US Customary    112 ft3

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. Similarly, million board-feet can be abbreviated as MMFBM, MMBFT, or MMBF.

FBM multiples
mfbm=thousand board-feet
mmfbm=million board-feet

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:

  • 1 ft × 1 ft × 1 in
  • 12 in × 12 in × 1 in
  • 30.48 cm × 30.48 cm × 2.54 cm
  • 144 in3
  • 1⁄12 ft3
  • 2360 cm3
  • 2.360 liters
  • 0.002360 cubic meters or steres
  • 1/1980 Petrograd Standard of board

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 2 × 4 lumber one would buy at a large lumber retailer. The 2 × 4 is actually only 1 12 in × 3 12 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.

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 14 inch for dimensions under 2 inches (51 mm); subtract 12 inch for dimensions under 8 inches (203 mm); and subtract 34 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]

See also


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