A board foot is the unit hardwood lumber is bought and sold by in North America. One board foot is a volume of 144 cubic inches of wood. The classic mental picture is a board that is 1 inch thick, 12 inches wide, and 1 foot (12 inches) long: 1 × 12 × 12 = 144 cubic inches = exactly one board foot.
It is important to understand that a board foot measures volume, not surface area or length. Two boards can look completely different and still contain the same number of board feet. A piece 1″ × 12″ × 1 ft and a piece 2″ × 6″ × 1 ft both equal one board foot, because both enclose 144 cubic inches. That is exactly why the unit exists: it lets a lumberyard price wildly different sizes of rough lumber fairly, by volume.
Every dimension goes in inches. If you have a length in feet, multiply by 12 first (8 ft = 96 in). For more than one identical board, multiply the result by the quantity. The 144 in the denominator is simply the number of cubic inches in one board foot.
| Board | Math | Board feet |
|---|---|---|
| 1″ × 12″ × 1 ft | (1 × 12 × 12) ÷ 144 | 1.00 bf |
| 2″ × 6″ × 1 ft | (2 × 6 × 12) ÷ 144 | 1.00 bf |
| 2″ × 6″ × 8 ft | (2 × 6 × 96) ÷ 144 | 8.00 bf |
| 1″ × 6″ × 8 ft | (1 × 6 × 96) ÷ 144 | 4.00 bf |
Notice the first two rows: same board foot count, totally different shape. The third board has twice the thickness and eight times the length of a one-board-foot piece, so it holds eight board feet.
Because hardwood is priced per board foot, knowing the count lets you compare lumber honestly and budget a project. A yard quoting $6.50 per board foot will charge about $52.00 for those 8.00 board feet of 2″ × 6″ × 8 ft stock. Without board feet, you would be comparing apples to oranges every time the dimensions changed.
Try the free Board Foot Calculator →The calculator above does this math instantly, adds a metric input option, and totals a whole project with a cut list. It runs entirely in your browser — no account, nothing uploaded. If you want the step-by-step method, see how to calculate board feet.