How it works
A board foot is 144 cubic inches. The calculator multiplies the three dimensions and the number of boards to get the volume, then divides by 144 cubic inches.
Volume = Thickness × Width × Length × Number of boards
Board feet = Volume in cubic inches ÷ 144
= Thickness (in) × Width (in) × Length (ft) ÷ 12 × Number of boards
Because the conversion goes through volume, you can mix units – inches for the cross-section and feet or meters for the length – and get the same answer.
Worked example
Inputs
- Board thickness
- 2 in
- Board width
- 6 in
- Board length
- 12 ft
- Number of boards
- 1
Result
- Board feet
- 12
- Volume
- 1 cu ft
Common mistakes
- Mixing nominal and actual sizes. Calculating on actual size while your supplier prices on nominal (or the other way round) makes price comparisons wrong.
- Entering the length in inches by mistake. 8 in instead of 8 ft gives a result twelve times too small – check the unit menu.
- Counting the board feet of one board and forgetting the quantity.
- Assuming board feet tells you coverage. Board feet measure volume, not the area a board will cover.
Assumptions and limits
- Every board in the stack has the same thickness, width and length. For mixed sizes, calculate each size separately and add the results.
- One board foot is 144 cubic inches (12 × 12 × 1 in), as defined by the University of Wisconsin–Madison Division of Extension.
- The calculator uses exactly the dimensions you enter; it does not convert nominal to actual sizes or add waste.
Frequently asked questions
What is a board foot?
A board foot is a volume of 144 cubic inches – a piece 12 in wide, 12 in long and 1 in thick, or any other shape with the same volume.
How do I calculate board feet by hand?
Multiply thickness in inches × width in inches × length in feet, divide by 12, and multiply by the number of boards. A board 1 in thick, 8 in wide and 10 ft long is 1 × 8 × 10 ÷ 12 ≈ 6.67 board feet.
Can I enter metric sizes?
Yes. Switch to metric and enter millimeters and meters; the calculator converts to cubic inches using 1 in = 2.54 cm and divides by 144.
Should I use nominal or actual sizes?
Use whatever your supplier prices on so the result matches their invoice. If you want the true volume of wood, measure the boards and use actual sizes.
Sources
- Measuring Wood: Board Feet (FEM-042) — University of Wisconsin–Madison Division of Extension. One board foot = 144 cubic inches (12 × 12 × 1 in).
Method reviewed November 2, 2026