Board Foot Calculator

A board foot is a volume unit equal to 144 cubic inches, the amount of wood in a piece one inch thick, twelve inches wide, and one foot long. Because hardwood boards leave the sawmill in random widths and lengths, volume rather than length is the fair basis for pricing, so the standard calculation is thickness in inches times width in inches times length in feet, divided by twelve. Thickness is quoted in quarters of an inch: 4/4 is nominal one inch, 5/4 is 1.25 inches, 8/4 is two inches. These are rough sawn dimensions, so a 4/4 board surfaced on two sides usually finishes near 13/16 inch while still being tallied and billed as a full inch. Grading under National Hardwood Lumber Association rules is based on the yield of clear cuttings taken from the poorer face. FAS requires boards at least 6 inches wide and 8 feet long yielding about 83 percent clear, Number 1 Common requires roughly 67 percent, and Number 2 Common about 50 percent, which means a lower grade at a lower price per board foot can deliver similar usable wood on projects built from short parts. Typical United States prices run about 3 to 7 dollars per board foot for red oak and poplar, 6 to 12 for cherry and white oak, and 10 to 18 for walnut and hard maple, with wide and thick stock carrying premiums. Add 15 to 25 percent for waste from defects, saw kerf, and milling, and remember that board footage measures rough lumber volume, not finished surface coverage.

Measuring sawn wood by the board foot developed in North American mill towns during the nineteenth century, when timber was cut from mixed hardwood forests and sold in random widths. Buyers first needed a way to estimate how much lumber a standing log would yield, which produced the competing log rules still printed on scale sticks: the Doyle rule, dating from the 1820s, the Scribner rule published by J. M. Scribner in 1846, and the International 1/4-inch rule developed by Judson Clark in 1906, which models saw kerf and log taper far more accurately than its predecessors. All three report their answer in board feet, which cemented the unit as the working currency of the lumber trade. Grading and dimensional standards followed. The National Hardwood Lumber Association was founded in 1898 to settle disputes between buyers and sellers by publishing uniform inspection rules, and its clear cutting grades of FAS, Select, and the Common grades remain in use across North America today. Softwood took a different route: a series of simplified practice conferences convened by the United States Department of Commerce from the 1920s standardized construction lumber into fixed nominal sizes and progressively reduced the dressed dimensions, which is why a nominal two by four now measures 1.5 by 3.5 inches. That effort eventually became the American Softwood Lumber Standard PS 20, first issued in 1970. Hardwood was never standardized into fixed widths, so it continues to be sold by the board foot.