What a board foot is
A board foot is a unit of lumber volume equal to 144 cubic inches — a piece 1 inch thick, 12 inches wide and 12 inches long. The formula is board feet = thickness (in) × width (in) × length (ft) ÷ 12. A 1×6 board 8 feet long is 1 × 6 × 8 ÷ 12 = 4 board feet. Sheet goods and flooring are sold by area instead, measured with the square footage calculator.
How to use this calculator
Enter the thickness and width in inches, the length in feet, and the quantity of identical pieces. The result shows total board feet and board feet per piece. Use nominal dimensions (what lumber is sold as) unless your supplier prices on actual size. For decking specifically, the deck boards calculator counts pieces rather than volume.
Why lumber is priced by board foot
Hardwood and rough lumber are usually sold by the board foot rather than by the piece, because it fairly prices boards of different sizes by volume. Multiply total board feet by the price per board foot to budget a project. Softwood framing lumber is more often sold per piece at standard lengths. Framing lumber is easier to count in the stud calculator.
Nominal vs. actual size
A "2×4" is nominal — its actual dimensions are about 1.5 × 3.5 inches after drying and planing. Most board-foot pricing uses nominal size, but confirm with your supplier, since calculating on actual size gives a smaller (and different) board-foot figure.
Frequently asked questions
- How do I calculate board feet?
- Multiply thickness in inches by width in inches by length in feet, then divide by 12. A 1×6 board 8 ft long is 1 × 6 × 8 ÷ 12 = 4 board feet.
- What is a board foot?
- A board foot is 144 cubic inches of lumber — the volume of a board 1 inch thick, 12 inches wide and 1 foot long.
- Is board foot the same as a linear foot?
- No. A linear foot measures length only; a board foot measures volume (thickness × width × length). Two boards of the same length can have different board feet.
- Should I use nominal or actual dimensions?
- Most lumber is priced on nominal size (e.g. a 2×4), so use nominal unless your supplier specifies actual, planed dimensions.
- How do I convert board feet back to linear feet?
- Divide the board feet by thickness times width divided by 12. Four board feet of 1x6 stock is 4 divided by 0.5, or 8 linear feet.