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How the Board Foot Calculator works
A board foot calculator tells you how much lumber you are buying by volume, the unit hardwood dealers and many lumberyards price by. Enter thickness, width and length, how many boards, and optionally the price per board foot; you get board feet per board and in total, the cost, linear feet and cubic volume.
One board foot is 144 cubic inches: a board 1" thick, 12" wide and 12" long. Board feet = thickness (in) × width (in) × length (ft) ÷ 12. By convention you use nominal sizes, so a 2×4 counts as 2" × 4", and hardwood thickness is given in quarters (4/4 = 1", 8/4 = 2"). Multiply by the number of boards, then by the price per board foot for the cost.
Example: four boards of 8/4 hardwood, 6" wide and 10 ft long, at $7.50 per board foot. One board is 2 × 6 × 10 ÷ 12 = 120 ÷ 12 = 10 board feet, so four are 40 board feet and cost 40 × $7.50 = $300. That is also 40 linear feet and 40 ÷ 12 = 3.33 cubic feet.
Hardwood is usually sold by its rough thickness, so surfaced 4/4 stock that measures about 13/16" is still figured as 1". With random-width boards, measure each one or use the average width. Buy extra for knots, checks and offcuts; woodworkers often add 20% to 30%. In metric, one board foot is about 0.00236 m³ (roughly 424 board feet per cubic meter).
Board Foot Chart: common sizes at a glanceFrequently asked questions
What is a board foot?
A board foot is a volume of lumber equal to 144 cubic inches: 1" thick, 12" wide and 12" long. A 1×12 or a 2×6 that is one foot long is one board foot. Hardwood and some softwood lumber is priced per board foot.
How do you calculate board feet?
Multiply thickness (in) × width (in) × length (ft) and divide by 12. If all three are in inches, divide by 144 instead. For example, a 2×4 that is 8 ft long is 2 × 4 × 8 ÷ 12 = 5.33 board feet, and ten of them are 53.33.
How many board feet are in a 2×4?
Using the nominal size, a 2×4 has 2 × 4 ÷ 12 = 0.667 board feet per foot of length. That makes 5.33 board feet in an 8 ft 2×4, 6.67 in a 10 ft and 8 in a 12 ft.
What do 4/4 and 8/4 mean in lumber?
Hardwood thickness is given in quarters of an inch: 4/4 ("four quarter") is 1", 5/4 is 1 1/4", 6/4 is 1 1/2" and 8/4 is 2". These are rough thicknesses before planing, and board feet are figured from them. You can type 8/4 straight into the thickness field.
What is the difference between board feet and linear feet?
Linear feet measure length only; board feet also account for thickness and width. For a 1×12 or a 2×6 the two numbers are the same, but a 2×4 has only 0.667 board feet per linear foot and a 2×12 has 2. The calculator shows both.