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What Is a Board Foot?
A board foot (BF) is a unit of volume used for measuring lumber. One board foot equals a piece of wood 12 inches long, 12 inches wide, and 1 inch thick, or 144 cubic inches. Board feet are the standard unit for pricing hardwood lumber and calculating quantities for woodworking and construction projects.
Unlike linear feet (which measure only length), board feet account for all three dimensions. This makes it a more accurate measure for comparing lumber of different sizes and calculating how much wood a project actually requires.
Board Foot Formula
Nominal vs. Actual Sizes
| Nominal Size | Actual Size | BF per Linear Foot |
|---|---|---|
| 1 x 4 | 3/4" x 3-1/2" | 0.333 |
| 1 x 6 | 3/4" x 5-1/2" | 0.500 |
| 1 x 8 | 3/4" x 7-1/4" | 0.667 |
| 2 x 4 | 1-1/2" x 3-1/2" | 0.667 |
| 2 x 6 | 1-1/2" x 5-1/2" | 1.000 |
| 2 x 8 | 1-1/2" x 7-1/4" | 1.333 |
| 2 x 10 | 1-1/2" x 9-1/4" | 1.667 |
| 2 x 12 | 1-1/2" x 11-1/4" | 2.000 |
| 4 x 4 | 3-1/2" x 3-1/2" | 1.333 |
Common Lumber Lengths
Standard lumber lengths are available in 2-foot increments: 8, 10, 12, 14, 16, 18, and 20 feet. Some lumberyards carry 6-foot and 24-foot lengths as well. When planning a project, try to minimize waste by selecting lengths that allow efficient cutting.
Frequently Asked Questions
How many board feet in a 2x4x8?
A 2x4 that is 8 feet long contains (2 x 4 x 8) / 12 = 5.33 board feet when calculated using nominal dimensions. Note that lumber is always priced and measured using nominal (not actual) dimensions.
How many 2x4s do I need for a wall?
For standard 16-inch on-center framing, you need one stud for each 16 inches of wall length, plus one. For an 8-foot wall, that is (8 x 12 / 16) + 1 = 7 studs. Add top plate (2) and bottom plate (1) pieces, corner studs, and headers for openings. A good rule of thumb is 1 stud per linear foot of wall.
Is board foot pricing based on nominal or actual size?
Board foot calculations use nominal dimensions (the stated size, such as 2x6), not the actual milled dimensions (1.5" x 5.5"). This is the industry standard for both softwood and hardwood pricing.