Board feet are a volume measurement used for rough lumber/timber. The idea is simple: one board foot equals a piece 1 inch thick, 12 inches wide, and 12 inches long.
Board Foot Formula
Use this formula when measurements are in inches and feet: thickness in inches x width in inches x length in feet, divided by 12.
For multiple boards, multiply the result by the quantity. Add a waste allowance when you expect knots, defects, milling loss, or layout offcuts.
Practical Example
A board that is 2 inches thick, 8 inches wide, and 10 feet long is 13.33 board feet because 2 x 8 x 10 / 12 = 13.33.
If you need five boards that size, the total is about 66.67 board feet before waste.
Common Mistakes
The biggest mistake is using nominal dimensions when the board has already been surfaced smaller. Use actual thickness and width for buying and cost estimates whenever possible.
Also check the length unit carefully. In the common imperial formula, thickness and width are in inches, but length is in feet.
FAQs
Is a board foot the same as a linear foot?
No. A board foot measures volume, while a linear foot measures length only.
Should I add waste to board feet?
Usually yes. Waste depends on material quality, milling, joinery, grain selection, and how tightly parts can be nested.
Estimates only
These results are estimates only. Verify measurements, material specifications, structural requirements, safety requirements, and local building rules before buying materials or building.