Board Feet Explained: How Lumber Is Measured and Priced
October 21, 2026
A board foot is a unit of lumber volume equal to a piece 1 inch thick, 12 inches wide, and 12 inches long: 144 cubic inches. Hardwood lumber, such as oak, walnut, and maple, is commonly priced per board foot, while construction lumber like 2×4s is usually sold per piece or per linear foot. Knowing the board-foot formula lets you compare prices fairly and order the right amount for a furniture or woodworking project.
The formula is board feet = thickness (in) × width (in) × length (ft) ÷ 12. Equivalently, thickness × width × length in inches ÷ 144.
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A rough-sawn board 1 inch thick, 6 inches wide, and 8 feet long contains 1 × 6 × 8 ÷ 12 = 4 board feet. A 2 × 10 that is 12 feet long (using nominal dimensions) contains 2 × 10 × 12 ÷ 12 = 20 board feet. A 4/4 (four-quarter, meaning 1-inch) hardwood board 8 inches wide and 10 feet long is 1 × 8 × 10 ÷ 12 = 6.67 board feet.
If a supplier charges $9 per board foot, that last board costs 6.67 × $9 = $60.
Nominal vs. Actual Dimensions
Construction lumber is named with nominal dimensions that are larger than the actual size after planing. A '2×4' measures 1½ by 3½ inches. Board-foot volume of retail softwood is usually calculated with nominal sizes: an 8-foot 2×4 counts as 2 × 4 × 8 ÷ 12 = 5.33 board feet. Using actual size, it holds only 1.5 × 3.5 × 96 ÷ 144 = 3.5 board feet of wood.
That difference is why a stack of 2×4s contains less wood than its nominal count suggests. Hardwood is usually sold rough, by the thickness in quarters of an inch (4/4, 5/4, 8/4), and its size shrinks when you surface it.
| Board | Nominal board feet | Actual wood (board feet) |
|---|---|---|
| 2x4, 8 ft | 5.33 | 3.50 |
| 2x6, 8 ft | 8.00 | 5.50 |
| 2x10, 12 ft | 20.00 | 13.88 |
| 1x6, 8 ft | 4.00 | 2.75 |
Planning a Project
For a woodworking project, make a cut list, calculate the board feet of each part in finished dimensions, add them up, and then increase the total by 15% to 30% for waste. The allowance depends on grain matching, defects, knots, and the number of cuts. Furniture grade work with careful color matching might need 30% or more extra.
A table with a top 1 inch thick, 36 inches wide, and 72 inches long has 1 × 36 × 72 ÷ 144 = 18 board feet. Add legs and aprons, say 8 more board feet, for 26 total, and order 32 to 34 allowing for waste.
Comparing Prices
To compare different sources, convert each to a price per board foot. A 1×6×8 pine board at $12 is $3.00 per nominal board foot. An 8-foot 2×4 priced at $4.50 is $0.84 per board foot. Rough hardwood at $7 to $12 per board foot for common species is often cheaper than pre-surfaced boards from a home center, which carry a premium for milling and convenience.
Check that the supplier states whether the price is for rough or surfaced stock, and whether the thickness is quoted in quarters.
Buying Tips
Examine boards for warp, cracks, and knots before buying. Allow your lumber to acclimate in your shop for a week or two, because moisture content affects how it moves after cutting. Ask whether the lumber is kiln-dried. Buy a little extra of the same species and batch to ensure color consistency across the project.
Frequently Asked Questions
How many cubic inches are in a board foot?
144 cubic inches.
How do I calculate board feet?
Thickness in inches × width in inches × length in feet, divided by 12.
Why is a 2x4 not 2 inches by 4 inches?
The name is nominal. After drying and planing, the actual size is 1½ by 3½ inches.
How much extra lumber should I buy?
Typically 15% to 30%, depending on the quality of the lumber and the complexity of the project.
What does 4/4 mean?
Four-quarter stock, which starts at 1 inch thick before surfacing.