Board foot calculator
This is arithmetic on the sizes you enter. Yards differ on whether they charge by nominal or actual size and how they round, so use this as an estimate and confirm the tally at the till.
Enter the thickness, width and length of a board and how many you have. The tool works out the board footage — the standard measure of lumber volume — adds a waste factor, and shows the equivalent cubic volume alongside it.
Worked example
A board 1 inch thick, 6 inches wide and 8 feet long is (1 × 6 × 8) ÷ 12 = 4 board feet. Ten of them is 40 board feet; add 10% for defects and cutting and you would buy around 44 board feet of rough stock to be safe.
The formula
board feet = (thickness_in × width_in × length_ft) ÷ 12
A board foot is 144 cubic inches. Thickness and width are in inches and length in feet, so dividing by 12 (rather than 144) accounts for the feet-to-inches on the length. In metric there is no board foot, so the tool converts your sizes to inches and feet to keep the yard's unit while also giving you cubic metres.
Questions
- What is a board foot?
- A board foot is a volume of lumber: 144 cubic inches, or a piece 12 inches by 12 inches by 1 inch thick. It is how rough hardwood is priced. A board 1 inch thick, 6 inches wide and 8 feet long is (1 × 6 × 8) ÷ 12 = 4 board feet, whatever its actual finished size.
- How do I calculate board feet?
- Multiply thickness in inches by width in inches by length in feet, then divide by 12. Or use inches throughout and divide by 144. Multiply by the number of identical boards. This tool does it either way you enter, and adds a waste factor for defects and cutting.
- Do I use nominal or actual size?
- Rough lumber is usually priced on its rough sawn size, which is close to nominal — a rough 1-inch board really is about an inch. Surfaced (S4S) lumber is smaller than its nominal call-out, but is still often sold by the nominal board foot. Ask the yard which they charge on, and enter that size.
- How is board foot different from a linear foot?
- A linear foot is just length; a board foot accounts for thickness and width as well, so it measures the amount of wood. Two boards the same length can be very different board footage if one is wider or thicker. Trim and moulding sell by the linear foot; rough boards sell by the board foot.
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