What a board foot is — the ÷12 lumber formula and 144-cubic-inch definition
A board foot is a volume — one square foot of board, one inch thick (144 in³). Board feet = thickness(in) × width(in) × length(ft) ÷ 12, so a 2×4×8 is 5.33 BF.
What this diagram shows
A diagram defining the board foot. On the left, a block of lumber one foot wide, one foot long, and one inch thick is labeled one board foot, equal to 144 cubic inches — a board foot is a volume, not a length or an area. On the right, the formula: board feet equals thickness in inches times width in inches times length in feet, divided by 12; the divide-by-12 reconciles the foot of length with the 144-cubic-inch board foot. A worked example shows a 2 by 4 by 8 feet equals 2 times 4 times 8 divided by 12 equals 5.33 board feet, figured on the named 2 by 4 rather than the 1½ by 3½ it actually measures.
Board Foot Calculator
Free board foot calculator: build a lumber cut list and get total board feet, MBF, pieces and linear feet. Nominal sizes or custom hardwood, no signup.
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