Formula
Board feet = thickness (in) × width (in) × length (ft) ÷ 121 board foot = 144 in³ = 1/12 ft³ ≈ 2.36 L How it works
A board foot is a volume: a piece one inch thick, twelve inches wide and one foot long, or 144 cubic inches. Hardwood dealers price almost everything by the board foot, so it is the number you need to compare offers.
Rough-sawn hardwood is sold by its thickness in quarters of an inch — 4/4 is 1 inch, 8/4 is 2 inches — measured before planing. Dimensional softwood such as a 2×6 is named by its nominal size even though it is actually 1.5 × 5.5 inches; board-foot pricing uses the nominal figures.
Plan for 20–30% extra when buying rough lumber for furniture, to allow for knots, checks and cutting the boards to clean lengths.
Frequently asked questions
How many board feet are in a 2×4×8?
2 × 4 × 8 ÷ 12 = 5.33 board feet.
Is a board foot the same as a linear foot?
No. A linear foot is just length, regardless of the board’s width and thickness. Trim and mouldings are sold by the linear foot; hardwood stock by the board foot.