What Is a Board Foot?
Part of Interior & Finishes
Quick answer
A board foot (bd ft) is the standard unit for selling hardwood lumber: a volume measuring 1 inch thick × 12 inches wide × 1 foot long, equal to 144 cubic inches. Calculate it as (thickness in × width in × length ft) ÷ 12.
Hardwood is sold by the board foot because boards come in random widths and lengths — you can't price them per piece. The board foot measures the actual volume of wood so a wide plank costs more than a narrow one of the same length.
The formula
Board feet = (Thickness in × Width in × Length ft) ÷ 12
Example: a 1 in × 6 in × 8 ft board is (1 × 6 × 8) ÷ 12 = 4 board feet. A board foot is always 144 cubic inches no matter how those dimensions are arranged.
The quarter (4/4) system
Rough hardwood thickness is written in quarters of an inch. Lumber is sold this way because it's milled thicker than the finished board to allow for planing.
| Called | Rough thickness |
|---|---|
| 4/4 (four-quarter) | 1 in |
| 5/4 | 1.25 in |
| 6/4 | 1.5 in |
| 8/4 | 2 in |
Use the board foot calculator to total an order and multiply by a price-per-board-foot for cost.
FAQs
What does bd ft mean?
Bd ft is the abbreviation for board feet, the volume unit for lumber. Some suppliers also write it as BF or bf.
Is a board foot the same as a linear foot?
No. A linear foot measures only length; a board foot measures volume (thickness × width × length). Two boards of equal length can have very different board-foot counts.