Lumber Board Feet Calculator

A board foot is a volume unit equal to 144 cubic inches, the amount of wood in a piece 1 inch thick, 12 inches wide and 1 foot long. Multiplying thickness in inches by width in inches by length in feet and dividing by 12 falls straight out of that definition. The unit exists because hardwood and rough sawn stock arrive in random widths and lengths, so pricing per piece or per linear foot would be meaningless. A supplier quoting 7 dollars per board foot for red oak is quoting a price per unit volume that holds across a mixed pile. Hardwood thickness is quoted in quarters of an inch as it came off the saw: 4/4 is nominally 1 inch, 5/4 is 1.25, 6/4 is 1.5 and 8/4 is 2 inches. Board footage is figured on that rough thickness even after surfacing removes material, so a surfaced 4/4 board measuring about 13/16 inch is still tallied and paid for as 1 inch. Under National Hardwood Lumber Association rules, width is measured to the nearest inch and length to the nearest foot, and grade is assigned from the yield of clear cuttings. Typical prices per board foot run about 4 to 7 dollars for red oak, 5 to 8 for hard maple and 8 to 15 for black walnut, with wide or figured stock well above that. Softwood dimensional lumber is the exception, tallied on nominal size, so a nominal 2 by 4 counts as 0.667 board feet per linear foot despite measuring 1.5 by 3.5 inches.

The board foot grew out of the North American sawmill trade in the eighteenth and nineteenth centuries, when lumber was tallied by the square foot of 1 inch thick boards. The term simply generalized that count to other thicknesses. Britain took a different path with the Hoppus foot, a measure published by Edward Hoppus in 1736 that deliberately understates round timber volume in order to approximate the squared timber recoverable from it, and most of the world now trades sawn wood in cubic meters. The measure only became consistent when grading did. The National Hardwood Lumber Association was founded in 1898 in Chicago, at a point when nearly every mill and buyer used its own inspection practice, and its rules fixed how thickness, width and length are measured and how surface measure converts into board footage. Those rules, revised regularly since, remain the basis on which hardwood is bought and sold in North America. Softwood took a parallel route through the American Lumber Standards, first issued in 1924 after a long dispute over dressed sizes and now maintained as Voluntary Product Standard PS 20, which fixed nominal designations while allowing actual planed dimensions to shrink, most notably in the 1964 revision that set the dry 2 by 4 at 1.5 by 3.5 inches.