Lumber Calculator
Calculate board feet, linear feet, and lumber costs for framing, decking, and woodworking projects.
Lumber Dimensions
Pricing (Optional)
Total Board Feet
44.4 BF
10 pieces @ 8 ft
How to Calculate Board Feet
Board feet (BF) is the standard unit for measuring lumber volume in North America. One board foot equals a board 1 inch thick, 12 inches wide, and 12 inches long (144 cubic inches).
Board Feet Formula
Board Feet = (Width × Thickness × Length) ÷ 12
All dimensions in inches, except length in feet. Example: A 2×4×8 board = (2 × 4 × 8) ÷ 12 = 5.33 board feet
Nominal vs Actual Lumber Sizes
| Nominal | Actual |
|---|---|
| 2×4 | 1.5\" × 3.5\" |
| 2×6 | 1.5\" × 5.5\" |
| 2×8 | 1.5\" × 7.25\" |
| 2×10 | 1.5\" × 9.25\" |
| 4×4 | 3.5\" × 3.5\" |
Common Lumber Types and Uses
Framing Lumber (2×4, 2×6, 2×8)
Used for wall studs, floor joists, rafters. Typically SPF (Spruce-Pine-Fir) or Douglas Fir. Studs are spaced 16\" or 24\" on center.
Dimensional Lumber (1×4, 1×6, 1×8)
For trim, shelving, light construction. Actual thickness is 0.75\". Common in pine, cedar, or poplar.
Posts and Beams (4×4, 6×6, 6×8)
Structural support for decks, pergolas, fences. Often pressure-treated for outdoor use.
Lumber Grading
- Stud Grade: Economy framing lumber
- #2 and Better: Standard construction grade
- #1: Higher quality, fewer knots
- Select Structural: Highest grade for visible applications
Calculating Studs for Framing
For 16\" on-center spacing: (Wall length in feet × 0.75) + 3
For 24\" on-center spacing: (Wall length in feet × 0.5) + 3
Add 3 for top plate, bottom plate, and end studs.
Important Notes
Lumber prices fluctuate significantly. Check local suppliers for current pricing. Pressure-treated lumber costs 20-40% more than untreated.
Always buy 10-15% extra lumber for cuts, mistakes, and warped boards. Inspect boards for straightness, excessive knots, and moisture content.
Green (wet) lumber shrinks as it dries. For precision work, use kiln-dried lumber with moisture content below 19%.
Frequently Asked Questions
How do you calculate board feet?
Board Feet = (Width in inches × Thickness in inches × Length in feet) ÷ 12. Example: A 2×4×8 board has (2 × 4 × 8) ÷ 12 = 5.33 board feet. Use actual dimensions (1.5\" × 3.5\") for precise calculations.
What is the actual size of a 2×4?
The actual size is 1.5\" × 3.5\". Nominal lumber sizes (the name you call it) are larger than actual dimensions after milling and planing. This applies to all dimensional lumber—always use actual sizes for precise construction plans.
How much does lumber cost per board foot?
Lumber prices vary widely by species and market conditions. Softwood framing lumber (pine, spruce, fir) costs $2-$4 per board foot. Hardwood (oak, maple, walnut) costs $5-$15/BF. Exotic hardwoods can exceed $20/BF. Prices peaked in 2021 but have since stabilized.
How many 2×4s do I need for framing?
For wall framing with 16\" on-center spacing: (Wall length in feet × 0.75) + 3 studs. Example: A 10 ft wall needs (10 × 0.75) + 3 = 10.5, round to 11 studs. This includes top/bottom plates and corner studs.
What's the difference between nominal and actual lumber sizes?
Nominal is the traditional name (2×4), while actual is the real milled size (1.5\" × 3.5\") after drying and planing. This sizing system developed because lumber was historically cut to nominal size when green, then shrank during drying and was planed smooth.