How this board foot calculator works
Each row multiplies thickness × width × length and divides by 144 (or by 12 when length is in feet), then multiplies by quantity. Rows are summed, so you can total a mixed order — a few 4/4 boards and a few 8/4 boards — in one pass.
This is a volume figure. It says nothing about the shape you can actually cut from a board: two 6-ft boards and one 12-ft board have the same board footage but very different usable lengths. For laying out actual parts against actual stock, use the cut list optimizer instead.
Sources
Board foot definition and formula: WoodWeb, "What is a Board Foot?". Nominal 2×4 actual dimensions (1.5 × 3.5 in.) are the standard S4S softwood sizing used throughout North American lumber yards.
Questions
What is a board foot?
A volume unit equal to 144 cubic inches — a board 12 in. long, 12 in. wide, and 1 in. thick. It's the standard unit hardwood is priced and sold by, because hardwood boards vary in width and length in a way that dimensional softwood lumber doesn't.
What is the board foot formula?
Thickness (in) × width (in) × length (ft) ÷ 12, or thickness × width × length in inches ÷ 144. This calculator uses actual measured thickness and width, and lets you enter length in feet or inches.
How many board feet in an 8 ft 2×4?
A construction 2×4 is nominal — its actual size is 1.5 × 3.5 in. So 1.5 × 3.5 × 8 ÷ 12 = 3.5 board feet, not 8 as the "2×4" name might suggest.
Rough or surfaced (S4S) thickness?
Hardwood is sold and tallied at its rough-sawn nominal thickness (4/4 = 1 in., 5/4 = 1.25 in., 8/4 = 2 in.), even after it's been planed thinner. Use the nominal thickness here to match a lumberyard quote, or the true thickness if you're estimating your own material.
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