How many board feet?

How do I calculate board feet?

Multiply the thickness and width in inches by the length in feet and divide by 12. A 2 × 4 that is 8 feet long is 2 × 4 × 8 ÷ 12 = 5.33 board feet; ten of them are 53.3 board feet. A board foot is a piece 12 by 12 inches and 1 inch thick — 144 cubic inches.

Do I use nominal or actual size for board feet?

Softwood lumber is sold by nominal size, so a 2 × 4 counts as 2 by 4 inches even though it measures 1½ by 3½. Rough hardwood is sold by thickness in quarters of an inch — 4/4 is 1 inch, 8/4 is 2 inches — and the actual width of each board.

How many board feet are in a 2 × 6 × 10?

2 × 6 × 10 ÷ 12 = 10 board feet. A 2 × 10 × 16 is 26.67, a 4 × 4 × 8 is 10.67, and a 1 × 6 × 8 is 4 board feet.

How do I figure the cost of lumber by the board foot?

Multiply the board feet by the price per board foot. At $4.50 a board foot, 26.67 board feet of 2 × 10 cost about $120. Enter the price above and the calculator totals every line.

How do I convert board feet to cubic meters?

One board foot is 0.00236 cubic meters, and one cubic meter is about 424 board feet. Switch to Metric to enter sizes in millimeters and meters and get cubic meters directly.

What does 4/4, 5/4 and 8/4 mean?

Rough hardwood thickness is named in quarters of an inch: 4/4 is 1 inch, 5/4 is 1¼ inches, 6/4 is 1½ inches and 8/4 is 2 inches. Enter the quarter-inch fraction as a decimal thickness, for example 1.25 for 5/4.

Is a board foot a measure of weight or length?

Neither. It is a volume of 144 cubic inches, the same as a piece 1 inch thick, 12 inches wide and 12 inches long. Two boards with the same board footage have the same volume of wood but may differ in weight, depending on species and moisture.

How the calculation works

One board foot is 144 cubic inches, which is the volume of a board 1 inch thick, 12 inches wide and 12 inches long. For a piece measured in inches of thickness and width and feet of length, board feet = thickness × width × length ÷ 12. The factor 12 turns the length from feet to inches and divides by the 144 cubic inches in a board foot. For softwood, the calculator uses the nominal size, which is how it is sold. In metric, the calculator multiplies the sizes in meters to get cubic meters; one board foot is 144 × 0.0254³ = 0.002360 cubic meters.

Worked example

A shopping list has 20 pieces of 2 × 4 × 8 ft studs, 6 pieces of 2 × 10 × 16 ft joists, 4 pieces of 8/4 oak, 7 in wide, 10 ft. Board feet by line: 2 × 4 × 8 ft studs: 2 × 4 × 8 ÷ 12 × 20 = 106.67; 2 × 10 × 16 ft joists: 2 × 10 × 16 ÷ 12 × 6 = 160; 8/4 oak, 7 in wide, 10 ft: 2 × 7 × 10 ÷ 12 × 4 = 46.67. The total is 313.33 board feet, or 0.739 cubic meters. At prices of $3.20, $3.60, $9.50 per board foot for the three lines, the cost is $341.33 + $576.00 + $443.33 = $1,360.67. The prices are illustrations only; use the ones from your supplier.

Common mistakes

• Entering length in inches. The length is in feet. A 96-inch board is 8, not 96.
• Using actual size for softwood and nominal for hardwood. Softwood is counted at nominal size (a 2×4 is 2 by 4), while rough hardwood is counted on the true thickness, in quarters, and the true width of each board.
• Not allowing for waste. Board feet measure what you buy. Cutting around defects and making kerfs means you need to buy more than the finished project contains.

Sources and related calculators

The inch-to-meter conversion (exactly 0.0254 m) is from NIST Handbook 44, Appendix C; the board foot as 144 cubic inches and the quarter-inch naming of rough hardwood thickness are standard lumber trade practice, as described above. Related: lumber calculator, deck calculator and cubic yard calculator.