How board feet work
A board foot is the volume of a board 1 inch thick, 12 inches wide and 1 foot long — 144 cubic inches, or about 2.36 liters. The formula is thickness (in) × width (in) × length (ft) ÷ 12, multiplied by the number of pieces. Hardwood lumber is priced per board foot, unlike construction lumber which is sold per piece.
Nominal thickness and the quarter system
Hardwood dealers describe thickness in quarters of an inch: 4/4 ('four quarter') is 1 inch, 5/4 is 1¼, 8/4 is 2 inches. Board feet are calculated from this rough-sawn nominal thickness even though surfaced boards measure less — a planed 4/4 board is about 13/16 inch thick but still sells as 1 inch. Enter the nominal thickness here to match the dealer's invoice.
Buying with waste in mind
Rough lumber hides defects: knots, checks, wane and warp all cost usable material. Furniture makers typically buy 15–30% more board feet than the cut list requires, more for high-grade projects where every part must be clear. Random widths and lengths at hardwood dealers also mean your parts won't nest perfectly.
Metric conversion
Outside North America, hardwood is sold by the cubic meter: one cubic meter is about 424 board feet. If a dealer quotes per m³, divide by 424 to compare with a per-board-foot price — and note whether the quote is rough-sawn or surfaced volume, since the difference is 20% or more.