How to Calculate Board Feet
A board foot (often abbreviated as BF or bd ft) is a specialized unit of volume used primarily in the lumber industry in the United States and Canada. Unlike linear feet, which only measure length, a board foot represents a precise volume of wood equal to 144 cubic inches. This is equivalent to a piece of wood that is exactly 12 inches wide, 1 foot long, and 1 inch thick.
- BF = Total Board Feet
- T = Thickness of the lumber (in inches)
- W = Width of the lumber (in inches)
- L = Length of the lumber (in feet)
Note: If you are measuring length in inches instead of feet, divide by 144 instead of 12.
Because hardwood lumber is sold by volume rather than by the piece, accurately calculating board feet is essential for estimating material costs for furniture, flooring, and cabinetry projects.
| Nominal Size | Actual Size (Approx.) | Length | Total Board Feet |
|---|---|---|---|
| 1x4 | ¾" × 3 ½" | 8 feet | 2.67 BF |
| 1x6 | ¾" × 5 ½" | 8 feet | 4.00 BF |
| 1x8 | ¾" × 7 ¼" | 8 feet | 5.33 BF |
| 2x4 | 1 ½" × 3 ½" | 8 feet | 5.33 BF |
| 2x6 | 1 ½" × 5 ½" | 8 feet | 8.00 BF |
| 4x4 | 3 ½" × 3 ½" | 8 feet | 10.67 BF |
Frequently Asked Questions
What is the difference between linear feet and board feet?
Linear feet measure only the straight-line length of a piece of wood, ignoring how thick or wide it is. Board feet measure the true volume of the wood. Softwoods used in construction (like standard 2x4s) are often sold by the linear foot or per piece, while valuable hardwoods are almost universally priced by the board foot.
What do lumber terms like 4/4 or 8/4 mean?
Hardwood thickness is commonly expressed in "quarters" of an inch. A board labeled 4/4 (pronounced "four-quarter") is exactly 1 inch thick rough-sawn, yielding about 3/4" to 13/16" after surfacing. An 8/4 board is 2 inches thick, and a 12/4 board is 3 inches thick. When using the calculator, treat 4/4 as 1 inch, 6/4 as 1.5 inches, and 8/4 as 2 inches.
Should I factor in extra board feet for waste?
Yes. It is highly recommended to add a waste factor to your total calculated board feet. Woodworking experts generally suggest adding 15% to 20% extra material to account for knots, checks, saw kerf loss, and the milling process required to square up rough lumber.