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Board Feet (total)
Common Lumber Sizes (Nominal vs Actual)
| Nominal Size | Actual Size (in) | Board Ft per 8ft piece | Common Use |
|---|---|---|---|
| 2x4 | 1.5" x 3.5" | 5.33 | Framing, studs |
| 2x6 | 1.5" x 5.5" | 8.0 | Exterior walls, joists |
| 2x8 | 1.5" x 7.25" | 10.67 | Floor joists, headers |
| 2x10 | 1.5" x 9.25" | 13.33 | Large headers, joists |
| 2x12 | 1.5" x 11.25" | 16.0 | Stairs, large headers |
| 4x4 | 3.5" x 3.5" | 10.67 | Posts, fence posts |
| 4x6 | 3.5" x 5.5" | 16.0 | Beams, pergola |
| 1x6 | 0.75" x 5.5" | 4.0 | Trim, siding, decking |
* Click any row to use those dimensions in the calculator above.
What is a Board Foot?
A board foot is a unit of lumber volume equal to 1 inch thick, 12 inches wide, and 12 inches long — or 144 cubic inches. Lumber is priced by board foot (BF) at lumber yards. The formula is: Thickness (in) x Width (in) x Length (ft) ÷ 12.
Board Feet = (Thickness × Width × Length) ÷ 12
Note that lumber is sold by nominal dimensions (like "2x4"), but the actual measurements are smaller. A 2x4 is actually 1.5" x 3.5". Board foot calculations should use nominal dimensions since that's how lumber is priced. Add 10-15% waste factor for cuts and mistakes on complex projects.