Nominal vs. Actual Lumber Sizes
Lumber is sold by nominal size (e.g., 2×4) but the actual dimension is smaller due to milling and drying. Always use actual dimensions when calculating board feet.
| Nominal | Actual | BF per 8 ft board |
|---|---|---|
| 2×4 | 1.5″ × 3.5″ | 3.5 BF |
| 2×6 | 1.5″ × 5.5″ | 5.5 BF |
| 2×8 | 1.5″ × 7.25″ | 7.25 BF |
| 2×10 | 1.5″ × 9.25″ | 9.25 BF |
| 2×12 | 1.5″ × 11.25″ | 11.25 BF |
| 4×4 | 3.5″ × 3.5″ | 8.17 BF |
Framing Lumber vs. Hardwood Pricing
Framing lumber (SPF, hem-fir, Douglas fir) is typically priced by the linear foot or per board at home centers. Hardwood (oak, maple, walnut, cherry) is priced by the board foot and sold at specialty lumber yards, often in random widths and lengths.
Frequently Asked Questions
What is the actual size of a 2x4?+
A 2×4 has actual dimensions of 1.5 inches × 3.5 inches. Lumber is sold by its nominal (pre-milling) size, but milling and drying reduce it. Always use actual dimensions when calculating board feet or planning cuts.
How much does lumber cost per board foot?+
Common softwood framing lumber (SPF 2×4) sells for $0.50–$0.80 per board foot at home centers. Hardwoods vary widely: poplar costs $3–$5/BF; oak is $5–$8/BF; walnut runs $10–$20/BF; figured maple or exotic species can exceed $30/BF.
How do I calculate how much lumber I need?+
For framing: calculate total linear feet needed for each member size, then convert to board count by dividing by your board length. For hardwood projects: calculate total board feet needed, add 15–20% waste, then divide by average BF per board in your lumber.
What is green lumber vs. kiln-dried?+
Green lumber is freshly cut and has high moisture content — it will shrink and warp as it dries. Kiln-dried (KD) lumber has been dried to 19% moisture or less and is more dimensionally stable. Use KD lumber for interior finish work; green or treated is fine for structural framing.