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Board feet for any lumber size and quantity, with cubic feet, MBF and the price at a per-board-foot rate.
With these inputs:
| Result | Value |
|---|---|
| Total board feet | 240 bf |
| Board feet per piece | 12 bf |
| Cubic feet | 20 cu ft |
| Thousand board feet (MBF) | 0.24 MBF |
| Formula | 2 × 6 × 12 ÷ 12 = 12 bf × 20 |
| Actual dressed size (PS 20) | 1.5 × 5.5 in — board feet still use 2 × 6 |
One board foot = 144 cubic inches (USDA Forest Products Laboratory Wood Handbook; NHLA rules). Softwood dimension lumber is tallied on its nominal size under the American Softwood Lumber Standard (PS 20), even though a dry 2x6 measures 1½ × 5½ in. Hardwood is measured on its actual rough size.
A board foot is a volume: 144 cubic inches, a board 1 inch thick, 12 inches wide and 1 foot long. Lumber yards and sawmills price hardwood, rough-sawn stock and large orders of framing by the board foot, so turning a lumber list into board feet is how you compare quotes. Enter the thickness and width in inches, the length in feet and how many pieces, and this gives the board feet per piece, the total, the cubic feet and the cost.
Multiply the thickness in inches by the width in inches by the length in feet, then divide by 12. A 2x6 that is 12 ft long is 2 × 6 × 12 ÷ 12 = 12 board feet. If you measure the length in inches, divide by 144 instead.
5.33 board feet: 2 × 4 × 8 ÷ 12. Softwood lumber is counted on its nominal size, so the fact that a dry 2x4 is really 1½ × 3½ in does not change the tally.
For softwood dimension lumber (2x4, 2x6, 4x4 and so on), the nominal size, under the American Softwood Lumber Standard. For hardwood, the actual rough size, measured in quarters of an inch: 4/4 is 1 in thick, 5/4 is 1¼ in and 8/4 is 2 in.
Twelve. A board foot is 144 cubic inches and a cubic foot is 1,728 cubic inches, so 1,728 ÷ 144 = 12. A thousand board feet (1 MBF) is 83.3 cubic feet.
Divide the price of a board by its board feet. A 2x8x16 is 21.33 board feet, so at $18 it costs about $0.84 a board foot. Comparing that figure across sizes shows which is really cheaper.
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