Board Foot Formula
BF = (Thickness in. × Width in. × Length ft) ÷ 12. Uses nominal dimensions. A 2×6×8 = (2 × 6 × 8) ÷ 12 = 8 board feet.
In Detail
The board foot formula uses nominal (not actual) dimensions. This means a surfaced 2×4 still calculates at 2" × 4" even though its actual dimensions are 1.5" × 3.5". Quick mental math: a 1×12 one foot long = 1 BF (the base unit). A 2×12 one foot long = 2 BF. Hardwood lumber is always sold by the board foot. Softwood framing is usually sold by the piece or linear foot, but contractors price large orders in BF for quantity discounts.