Board Foot Calculator
How many board feet of lumber you need, and what it costs at the yard’s price.
Good to know. A board foot is a board one inch thick and a foot square. A 2×4 is neither 2 nor 4 inches, but is priced as one.
How it works
In plain words
Multiply thickness and width in inches by the length in feet, and divide by 12. Multiply by the number of boards, and by the price per board foot for the cost.
The formula
board feet = thickness (in) × width (in) × length (ft) ÷ 12 1 board foot = 144 in³ ≈ 0.00236 m³
Worked example
A 2×6 that is 8 feet long holds 2 × 6 × 8 ÷ 12 = 8 board feet, so ten of them are 80 board feet, or 320.00 at 4.00 a board foot.
Sources
- NIST Special Publication 811, Guide for the Use of the International System of Units, Appendix B The inch is exactly 2.54 cm, so 144 cubic inches is 0.0023597 m³.
Sources checked October 3, 2026. 3 automated tests check its answers on every change.
About the board foot calculator
The board foot is how lumber, and especially hardwood, is sold in the US and Canada. One board foot is the volume of a board 1 inch thick, 12 inches wide and 12 inches long: 144 cubic inches. It lets a yard price boards of any size by volume.
The quick formula is thickness in inches, times width in inches, times length in feet, divided by 12. A 1×12 that is 1 foot long is exactly one board foot; a 2×6 that is 8 feet long is 8.
Use the nominal size, the one the board is sold as, not what the tape measure says. A 2×4 is really about 1½ by 3½ inches after drying and planing, but it is counted and priced as 2 by 4. Rough-sawn hardwood is sold by its thickness in quarters of an inch: 4/4 is 1 inch, 8/4 is 2 inches.
Buy 10–15% more than the plan needs to allow for defects, knots and cuts. Dimensional softwood at a big-box store is usually priced per piece rather than per board foot. For a deck, use the deck calculator.
Questions people ask
How do I calculate board feet?
Thickness (in) × width (in) × length (ft) ÷ 12. A 2×6 that is 8 feet long is 8 board feet.
How many board feet is a 2×4×8?
Five and a third: 2 × 4 × 8 ÷ 12 = 5.33 board feet.
Do I use the actual or nominal size?
The nominal size, which is how lumber is sold. Rough hardwood is measured in quarters of an inch, such as 4/4 or 8/4.