Board Feet Calculator
Calculate lumber board feet from thickness, width, and length.
Enter thickness, width, length, and quantity. Get total board feet plus optional cost based on per-board-foot price.
Board feet measures lumber volume. Formula: (thickness in × width in × length ft) / 12.
What a board foot is
A board foot is a unit of lumber volume equal to a board 1 inch thick, 12 inches wide, and 1 foot long (144 cubic inches). Lumber yards and mills price hardwood and rough-cut lumber per board foot. The formula is straightforward: (thickness in inches * width in inches * length in feet) / 12.
Nominal vs actual dimensions
Important: a "2x4" is nominally 2 inches by 4 inches but ACTUALLY 1.5 inches by 3.5 inches after planing. For pricing per board foot, lumber yards typically use the NOMINAL size, but you should confirm with your supplier. Rough-cut lumber (often hardwood) uses actual measured dimensions.
Common board-foot calculations
- 1x6 x 8 ft: (1 * 6 * 8) / 12 = 4 bf
- 2x4 x 8 ft (nominal): (2 * 4 * 8) / 12 = 5.33 bf
- 2x10 x 12 ft: (2 * 10 * 12) / 12 = 20 bf
- 4/4 (1 in) hardwood, 6 in wide, 10 ft: 5 bf
Hardwood quarter measurements
Hardwood is often sold in "quarters" representing thickness: 4/4 (one inch), 5/4 (1.25 inches), 8/4 (2 inches), etc. The width and length are still measured in inches and feet, then divide by 12 to get board feet. Quarter-sawn vs flat-sawn affects price but not the board-foot count.