Board feet explained

What a board foot is

A board foot is a volume of wood equal to a board 12" wide, 12" long, and 1" thick, or 144 cubic inches. Hardwood is commonly priced by the board foot.

The formula

Board feet = thickness (inches) × width (inches) × length (feet) ÷ 12. A board 1" × 6" × 8' is 1 × 6 × 8 ÷ 12 = 4 board feet. A board 2" × 8" × 10' is 13.33 board feet, which at $9 per board foot costs $120. The board feet calculator does this for any size and quantity.

Quarters: 4/4, 5/4, 8/4

Rough hardwood thickness is often given in quarters of an inch: 4/4 is 1" thick, 5/4 is 1 1/4", 6/4 is 1 1/2", and 8/4 is 2". Lumber is usually sold at its rough thickness, so the finished board will be thinner after surfacing. A 4/4 board often ends up around 13/16" thick.

Buying tips

Plan on extra for waste, commonly 10 to 20 percent, more for boards with defects. Construction lumber like 2×4s is often sold by the piece or by the linear foot, not by the board foot. Check actual sizes in the lumber size chart.