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Calculate board feet, volume, weight, and cost for dimensional and custom lumber sizes. Perfect for estimating lumber quantities for framing, decking, and woodworking projects.
Actual size: 1.5" × 3.5"
Where T = thickness (in), W = width (in), L = length (ft)
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A board foot is the standard unit of measurement for lumber volume in North America. It represents a piece of wood that is 1 foot long, 1 foot wide, and 1 inch thick.
This calculator helps you determine how many board feet you need for your project, whether you're buying dimensional lumber (2x4s, 2x6s) or custom-milled hardwoods.
1 board foot = 144 cubic inches = 1/12 cubic foot
Use the board foot formula to calculate lumber volume:
Important: Thickness and width should be in inches, while length should be in feet. For dimensional lumber, use the actual dimensions, not the nominal size.
10 pieces of 2×6: 8 ft long
Actual size: 1.5" × 5.5"
BF per piece = (1.5 × 5.5 × 8) / 12
BF per piece = 66 / 12 = 5.5 BF
Total = 10 × 5.5 = 55 BF
At $3.00/BF: 55 × $3.00 = $165.00
Lumber is sold by nominal size but is actually smaller due to drying and planing. A "2×4" is not 2 inches by 4 inches—it's actually 1.5" × 3.5".
Lumber starts at the nominal size when rough-cut from the log. After drying (which causes shrinkage) and planing (which removes material to create smooth surfaces), the final dimensions are smaller.
Complete nominal to actual size conversions with board feet per 8-foot length:
| Nominal Size | Actual Size (in) | BF per 8 ft | BF per 10 ft | BF per 12 ft |
|---|---|---|---|---|
| 1×4 | 0.75" × 3.5" | 1.75 BF | 2.19 BF | 2.63 BF |
| 1×6 | 0.75" × 5.5" | 2.75 BF | 3.44 BF | 4.13 BF |
| 1×8 | 0.75" × 7.25" | 3.63 BF | 4.53 BF | 5.44 BF |
| 1×12 | 0.75" × 11.25" | 5.63 BF | 7.03 BF | 8.44 BF |
| 2×4 | 1.5" × 3.5" | 3.50 BF | 4.38 BF | 5.25 BF |
| 2×6 | 1.5" × 5.5" | 5.50 BF | 6.88 BF | 8.25 BF |
| 2×8 | 1.5" × 7.25" | 7.25 BF | 9.06 BF | 10.88 BF |
| 2×10 | 1.5" × 9.25" | 9.25 BF | 11.56 BF | 13.88 BF |
| 2×12 | 1.5" × 11.25" | 11.25 BF | 14.06 BF | 16.88 BF |
| 4×4 | 3.5" × 3.5" | 8.17 BF | 10.21 BF | 12.25 BF |
| 4×6 | 3.5" × 5.5" | 12.83 BF | 16.04 BF | 19.25 BF |
| 6×6 | 5.5" × 5.5" | 20.17 BF | 25.21 BF | 30.25 BF |
A board foot measures volume (length × width × thickness), while a linear foot only measures length regardless of width or thickness. Board feet are used for pricing hardwoods and comparing lumber costs accurately.
Lumber is cut to nominal size when rough-sawn but shrinks during drying and becomes smaller after planing to create smooth surfaces. A 2×4 starts at 2" × 4" but ends up at 1.5" × 3.5" after processing.
Add 10-15% for typical projects to account for cutting waste, defects, and mistakes. For complex projects with many angles or premium work where you'll be selective about grain, add 20-25% extra.
Standard lengths are 8, 10, 12, 14, 16, 18, and 20 feet. Buy the longest length that minimizes waste for your project. For example, if you need 7-foot pieces, 14-foot boards give you two pieces with minimal waste.
Hardwood is often sold in random widths. Use the custom dimensions option to enter actual thickness (in quarters: 4/4 = 1", 5/4 = 1.25", 8/4 = 2") and width. The formula is the same: (T × W × L) / 12.
S2S means "Surfaced Two Sides" (faces are planed smooth), while S4S means "Surfaced Four Sides" (faces and edges are planed). Rough lumber is not surfaced and will be the full thickness stated.
Weight estimates assume air-dried lumber (12-15% moisture content). Green or freshly cut lumber can weigh 50-100% more due to water content. Actual weights also vary by species and individual boards.
Yes, pressure-treated lumber uses the same nominal/actual sizing as regular lumber. However, it weighs more due to the treatment chemicals and retained moisture. Add 20-40% to weight estimates for PT lumber.
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