Board feet (BF) is how lumber yards price and sell hardwood and rough-sawn lumber — it measures wood volume. But when you're building, you need to know how many linear feet of each board size to buy. This calculator converts board feet (volume) to linear feet (length) for any lumber dimension.
Critical: always use actual lumber dimensions, not nominal sizes. A 2×4 is actually 1.5 inches × 3.5 inches after planing and drying. Using nominal sizes (2×4) will underestimate the linear feet and leave you short on material.
Board Feet to Linear Feet
Convert lumber board feet to linear feet
Linear Feet
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What is a Board Foot?
A board foot is a unit of volume for lumber, equal to a piece of wood 12 inches long, 12 inches wide, and 1 inch thick — or any equivalent volume totaling 144 cubic inches. The formula is: Board Feet = (Length in ft × Width in inches × Thickness in inches) / 12.
The 144 Rule
One board foot = 144 cubic inches of wood. This is the fundamental constant behind all board foot calculations. To find board feet: multiply length (inches) × width (inches) × thickness (inches), then divide by 144. An 8-foot 2×4: (96 × 3.5 × 1.5) / 144 = 504 / 144 = 3.5 board feet. Most professionals use the shortcut: BF = (L ft × W in × T in) / 12.
Board Feet to Linear Feet Formula
To convert board feet (volume) to linear feet (length), you need to know the width and thickness of the lumber:
Always use actual lumber dimensions, not nominal sizes. A 2×4 is actually 1.5″ × 3.5″. A 2×6 is 1.5″ × 5.5″. A 1×6 is 0.75″ × 5.5″.
Example: Building a Deck Frame
You need 200 board feet of 2×8 lumber for deck joists. Actual dimensions: 1.5 inches × 7.25 inches. Linear feet = (200 × 12) / (7.25 × 1.5) = 2,400 / 10.875 = 220.7 linear feet. At standard 16-foot lengths, that's approximately 14 boards (220.7 / 16 = 13.8, round up). This real-world example shows why you can't just guess — 200 board feet of 2×8 sounds like a lot of wood, but it's only 14 sixteen-foot boards.
Worked Examples — Common Lumber Sizes
| Board Feet | Lumber Size | Actual W × T (in) | Linear Feet | Typical Project |
|---|---|---|---|---|
| 10 | 2×4 | 3.5 × 1.5 | 22.9 | Wall framing studs |
| 25 | 2×6 | 5.5 × 1.5 | 36.4 | Deck joists, exterior walls |
| 50 | 1×6 | 5.5 × 0.75 | 145.5 | Fence pickets, trim boards |
| 100 | 2×12 | 11.25 × 1.5 | 71.1 | Stair stringers, beams |
| 200 | 2×10 | 9.25 × 1.5 | 173.0 | Floor joists, headers |
Common Lumber Dimensions Reference — Nominal vs Actual
Lumber is sold by nominal dimensions (the rough-sawn size), but the actual dimensions are smaller after planing and kiln drying. Softwood construction lumber loses approximately 1/2 inch in thickness and 1/2 inch in width from nominal. Hardwood is typically sold in quarters of an inch (4/4 = 1 inch rough, planes to 3/4 inch).
| Nominal Size | Actual Size (in) | Cross-Section (sq in) | LF per 1 BF | BF in 8-ft board |
|---|---|---|---|---|
| 2×4 | 1.5 × 3.5 | 5.25 | 2.29 | 3.5 |
| 2×6 | 1.5 × 5.5 | 8.25 | 1.45 | 5.5 |
| 2×8 | 1.5 × 7.25 | 10.875 | 1.10 | 7.25 |
| 2×10 | 1.5 × 9.25 | 13.875 | 0.86 | 9.25 |
| 2×12 | 1.5 × 11.25 | 16.875 | 0.71 | 11.25 |
| 1×4 | 0.75 × 3.5 | 2.625 | 4.57 | 1.75 |
| 1×6 | 0.75 × 5.5 | 4.125 | 2.91 | 2.75 |
| 1×8 | 0.75 × 7.25 | 5.438 | 2.21 | 3.625 |
| 4×4 | 3.5 × 3.5 | 12.25 | 0.98 | 8.17 |
Note: hardwood lumber uses the quarter system — 4/4 = 1 inch rough (planes to ~3/4"), 5/4 = 1.25 inches rough (~1" finished), 8/4 = 2 inches rough (~1.75" finished). Hardwood width is random and measured in inches. Hardwood board foot pricing: (Thickness in inches × Width in inches × Length in feet) / 12.
When Lumber Yards Use Board Feet vs Linear Feet
Priced by Board Foot
Hardwood lumber (oak, maple, walnut, cherry, mahogany) is almost always priced per board foot. You'll see tags like "$4.50/BF" at the lumber yard. Rough-sawn softwood from small mills is also sold by the board foot. Specialty and exotic woods are always BF-priced because they come in random widths and lengths — the yard calculates the total volume of each piece.
Priced by Linear Foot
Dimensional lumber (2×4s, 2×6s, etc.) at home centers is priced per piece or per linear foot — board feet is too confusing for retail. Decking boards (5/4×6) are priced per linear foot. Trim and molding is always per linear foot. Treated lumber for outdoor use is priced per piece or LF. The rule: if it comes in standard lengths with a fixed cross-section, it's usually LF-priced.
The BF-to-LF conversion is most useful when you're buying hardwood for a furniture or flooring project, or rough-sawn lumber from a small mill. If you're buying dimensional lumber at Home Depot or Lowe's, you probably don't need this conversion — just count the boards you need by length. But if a lumber yard quotes you 150 board feet of 5/4×6 cedar decking at $3.25/BF, you need this calculator to know that's approximately 393 linear feet of decking.