What is a board foot?
A board foot is a unit of lumber volume equal to 144 cubic inches — for instance a piece 1 inch thick, 12 inches wide and 1 foot long. Because it measures volume, a 2×6×8 and a 1×12×8 hold the same number of board feet.
How do I calculate board feet?
- Thickness and width in inches, length in feet:
BF = T × W × L ÷ 12 - All three in inches:
BF = T × W × L ÷ 144 - Metric: volume in m³ = (Tmm/1000) × (Wmm/1000) × Lm, then divide by 0.002359737216 to get board feet.
Worked example: a 2 in × 4 in × 8 ft board is 2 × 4 × 8 ÷ 12 = 5.333 board feet.
Three of them come to 16 board feet.
How should I measure a board?
- Measure thickness and width across the face; measure length along the board.
- Enter fractions as you read the tape —
3/4or1 1/2— or switch to metric for millimetres. - Round rough or uneven stock to how you actually buy or cut it, and keep the basis consistent across a cut list.
Should I use actual or nominal dimensions?
A board sold as “2×4” is nominal; once surfaced it actually measures about 1.5 × 3.5 inches. Board foot is a volume, so the figure depends on which you enter. This tool never converts one to the other — pick Actual for surfaced sizes you measured, or Nominal for the sizes as called out, and the result tells you which basis it used.
Board foot vs log board foot — which one?
Use this calculator for finished, rectangular lumber where you know thickness, width and length. To estimate the lumber that can be sawn from a round log using the Doyle, Scribner or International 1/4-inch rules, use the Log Board Foot Calculator instead — those are estimates of yield, not a volume of a known board.
Frequently asked questions
Can I enter fractions?
Yes, in US mode: whole numbers, decimals, simple fractions like 3/4, and mixed numbers like 1 1/2. Metric mode uses decimals.
Does the calculator convert nominal to actual sizes?
No. It uses exactly the numbers you enter and labels the result as actual or nominal. It does not turn a 2×4 into 1.5×3.5.
How is the cubic-metre value derived?
From the exact definition: 1 board foot = 144 cubic inches = 0.002359737216 m³.
Is board foot the same as a linear or square foot?
No. A linear foot measures length only; a board foot measures volume (thickness × width × length).
Sources
- Board foot definition (144 in³) and the ÷ 144 formula: Ohio State University Extension (CFAES), Measuring Standing Trees.
- Exact inch and foot: NIST — SI units of length.