A board foot is the standard unit for purchasing hardwood lumber in North America. It equals 144 cubic inches of wood.
Formula
Board Feet = (Thickness × Width × Length) ÷ 144
All measurements in inches. Alternatively: (T × W × L in feet) ÷ 12.
Example
A board that is 2 inches thick, 6 inches wide, and 8 feet long: (2 × 6 × 96) ÷ 144 = 8 board feet.
Pricing
Lumber is priced per board foot. Cherry at $8/BF for the above board = $64. Softwood (pine, cedar) is usually sold by the linear foot instead.
Board Feet vs. Linear Feet
Softwood lumber (framing pine, cedar fencing) is typically priced by the linear foot regardless of thickness or width, while hardwoods (oak, walnut, cherry) are priced by the board foot because they're sold in varying, non-standard thicknesses. Confusing the two pricing systems when estimating a hardwood project is a common and costly mistake for first-time woodworkers.
Nominal vs. Actual Dimensions
A board sold as "1 inch thick" (4/4 in hardwood terminology) is typically closer to 13/16" after surfacing/planing — board foot calculations for pricing use the rough, pre-surfaced (nominal) dimension, not the final finished size, which can make actual usable material feel smaller than the board footage suggests.