Board Feet Calculator for Lumber
Enter the quantity and the thickness, width and length of each board size. Board feet are thickness x width x length / 12, with thickness and width in inches and length in feet. Leave size 2 at zero pieces if you only need one.
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Formula
board feet = quantity x thickness (in) x width (in) x length (ft) / 12
Board feet to buy = total board feet x (1 + waste / 100), rounded up. Cost = board feet to buy x price per board foot. Cubic feet = board feet / 12.
Assumptions
- Thickness and width are in inches, length is in feet. Use nominal sizes for priced softwood (a 2x4 is 2 by 4) or actual sizes if you want true wood volume.
- Two board sizes can be added together; set the second quantity to 0 to ignore it.
- Price is optional; with 0 the cost shows as 0.
Worked example
Ten 2x4x8 boards: 10 x 2 x 4 x 8 / 12 = 53.33 board feet. Four 2x6x12 boards: 4 x 2 x 6 x 12 / 12 = 48 board feet. Together 101.33 board feet. With 10 percent waste that is 111.47, so buy 112. At 1.25 per board foot the cost is 140.00.
Frequently asked questions
How do you calculate board feet?
Multiply thickness in inches by width in inches by length in feet, then divide by 12. One 2 x 4 that is 8 ft long is 2 x 4 x 8 / 12 = 5.33 board feet. A board foot is 144 cubic inches of wood.
Should I use nominal or actual dimensions?
Hardwood is sold by rough thickness in quarters of an inch, so use that. Softwood dimensional lumber is usually priced by the nominal size, so a 2 x 4 counts as 2 by 4 even though it measures about 1.5 by 3.5 inches. Using actual sizes gives the wood you really get, which is smaller.
How many board feet are in a 1 x 12 x 10 board?
1 x 12 x 10 / 12 = 10 board feet. A 1 x 12 board that is 1 ft wide and 1 inch thick has one board foot for every foot of length.
How do I get the cost of a lumber order?
Round the board feet with waste up to a whole number and multiply by the price per board foot. For 101.33 board feet plus 10 percent waste you buy 112, and at 1.25 per board foot that is 140.00.