Board foot calculator: board feet, linear feet, volume and cost for a stack of lumber, at nominal size and at the dressed size of a 2x4, 2x6 and more.
10 pieces of 2 × 6 in × 8 ft come to 80 board feet and 80 linear feet; the dressed wood is 55 BF.
One board foot is 144 in³: a piece 1 in thick, 12 in wide and 1 ft long.
Softwood is sold by nominal size; this is the wood you actually get.
A board foot is 144 cubic inches of wood, a piece 1 in thick, 12 in wide and 1 ft long. Board feet for a stack are thickness (in) × width (in) × length (ft) ÷ 12 × pieces. Linear feet are length × pieces, and cost follows the basis the yard prices by: per piece, per board foot or per linear foot.
The default, ten 2 × 6 boards 8 ft long, is 80 board feet and 80 linear feet, costing 75.00 at 7.50 each. Softwood board feet are counted on the nominal size, but a dry 2 × 6 is dressed to 1½ × 5½ in, so the wood delivered is 55 board feet.
Turn off nominal sizing for rough-sawn hardwood or metric timber, which is measured as it is. Metric pieces convert at 1 board foot = 2.359737216 litres.
Checked against: Hand calculation: 2 × 6 × 8 / 12 = 8 BF × 10 = 80; dressed 1.5 × 5.5 × 8 / 12 × 10 = 55 (PS 20 sizes)
Checked against: Definition: 1 BF = 144 in³ = 1 in × 12 in × 12 in; dressed 0.75 × 11.25 × 12 / 144 = 0.703125
Checked against: Python decimal: 0.05 × 0.15 × 3 × 20 = 0.45 m³ ÷ 0.002359737216 m³ per BF = 190.70; 60 m ÷ 0.3048 = 196.85 ft × 2
Multiply thickness in inches by width in inches by length in feet, then divide by 12. A 2 × 6 that is 8 ft long is 2 × 6 × 8 ÷ 12 = 8 board feet, so ten of them are 80. With all three sides in inches, divide by 144 instead: a board 1 × 12 × 12 in is exactly 1 board foot.
Nominal size for surfaced softwood: a 2 × 4 is counted as 2 × 4 in although it measures about 1½ × 3½ in. Hardwood is measured at its actual size, and rough hardwood thickness is given in quarters, 4/4 for 1 in and 8/4 for 2 in. With nominal sizing on, this calculator shows both: ten 2 × 6 × 8 ft are 80 BF nominal and 55 BF dressed.
1½ × 3½ in (38 × 89 mm) once dried and planed. Other 2× sizes lose ½ in of width up to 6 in and ¾ in above that: a 2 × 6 is 1½ × 5½, a 2 × 8 is 1½ × 7¼, a 2 × 10 is 1½ × 9¼ and a 2 × 12 is 1½ × 11¼ in. A nominal 1 in board is ¾ in thick, and a 4 × 4 is 3½ × 3½ in.
423.78. One board foot is 144 in³, exactly 2.359737216 litres, and 1 m³ ÷ 0.002359737216 m³ = 423.776. The metric example uses this: 20 pieces of 50 × 150 mm timber 3 m long are 0.45 m³, which is 190.70 board feet.
MBF means 1,000 board feet; MFBM and MBFT mean the same, and MMBF is a million board feet. A thousand board feet is 83.33 ft³, or 2.36 m³. A price of 600 per MBF is 0.60 per board foot, so an 8-board-foot 2 × 6 × 8 ft costs 4.80 at that rate.
Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 3 worked examples whose answers come from independent sources; for example, “Ten 2 × 6 × 8 ft at 7.50 each” is checked against Hand calculation: 2 × 6 × 8 / 12 = 8 BF × 10 = 80; dressed 1.5 × 5.5 × 8 / 12 × 10 = 55 (PS 20 sizes).
USDA Forest Products Laboratory — Wood Handbook (FPL-GTR-282), lumber sizes and measurement; Board foot — 144 in³, exactly 2.359737216 L; NIST Voluntary Product Standard PS 20 — American Softwood Lumber Standard (dressed sizes).
3 worked examples with independently sourced answers ship with this calculator. They run in the test suite; you can run them here too.
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