BF ↔ LF Calculator
Convert board feet to linear feet, or linear feet to board feet — for any lumber cross-section. Enter the thickness and width once, then read either direction. Handles 4/4–8/4 hardwoods and every dimensional 2×.
Cross-section first — set the thickness and width of the board, then enter the amount you know in either BF or LF. The formula: BF/LF = (T × W) ÷ 12. Use nominal dimensions for softwood (2×4 stays 2×4).
Tip: To convert a whole random-width pack, use the Batch mode on the main calculator — it sums every board's BF automatically.
The BF ↔ LF Formula
Board feet and linear feet are related but measure different things. A linear foot measures length; a board foot measures volume (144 cubic inches). The bridge between them is the cross-section area (thickness × width) of the board.
BF → LF (I have BF, need LF)
LF = BF ÷ ((T × W) ÷ 12)
Rearranged: LF = BF × 12 ÷ (T × W). Example: 40 BF of 4/4 × 8" oak → 40 × 12 ÷ (1 × 8) = 60 linear feet.
LF → BF (I have LF, need BF)
BF = LF × (T × W) ÷ 12
Example: 60 LF of 2×6 pine → 60 × (2 × 6) ÷ 12 = 60 BF. Notice how the numbers happen to be equal — this is because 2×6 gives exactly 1.0 BF per linear foot.
Multiplying by Quantity
The converter multiplies its result by the quantity you enter. If you have 20 identical 4/4 × 8" × 8' boards, that's (1×8×8)÷12 × 20 = 106.7 BF total.
BF per Linear Foot — Common Cross-Sections
Multiply "BF/LF" by the length in feet to get board feet. Nominal sizes shown for softwood; hardwood uses actual thickness (4/4 = 1", 8/4 = 2").
| Cross-section | Formula | BF per LF | 10 LF = ? |
|---|---|---|---|
| 4/4 × 4" | (1×4)÷12 | 0.333 | 3.33 BF |
| 4/4 × 6" | (1×6)÷12 | 0.500 | 5.00 BF |
| 4/4 × 8" | (1×8)÷12 | 0.667 | 6.67 BF |
| 4/4 × 10" | (1×10)÷12 | 0.833 | 8.33 BF |
| 4/4 × 12" | (1×12)÷12 | 1.000 | 10.00 BF |
| 5/4 × 6" | (1.25×6)÷12 | 0.625 | 6.25 BF |
| 6/4 × 8" | (1.5×8)÷12 | 1.000 | 10.00 BF |
| 8/4 × 8" | (2×8)÷12 | 1.333 | 13.33 BF |
| 1×4 (softwood, nominal) | (1×4)÷12 | 0.333 | 3.33 BF |
| 1×6 (softwood) | (1×6)÷12 | 0.500 | 5.00 BF |
| 2×4 (softwood) | (2×4)÷12 | 0.667 | 6.67 BF |
| 2×6 (softwood) | (2×6)÷12 | 1.000 | 10.00 BF |
| 2×8 (softwood) | (2×8)÷12 | 1.333 | 13.33 BF |
| 2×10 (softwood) | (2×10)÷12 | 1.667 | 16.67 BF |
| 2×12 (softwood) | (2×12)÷12 | 2.000 | 20.00 BF |
| 4×4 (softwood) | (4×4)÷12 | 1.333 | 13.33 BF |
| 4×6 (softwood) | (4×6)÷12 | 2.000 | 20.00 BF |
| 6×6 (softwood) | (6×6)÷12 | 3.000 | 30.00 BF |
BF ↔ LF in Real Projects
Example 1 — Buying Deck Joists by Piece vs BF
A yard quotes 2×8 × 12 ft at $22 per piece. Each is 16 BF, so effective price is $22 ÷ 16 = $1.38/BF. Compare with a hardwood dealer's $8/BF walnut — you can now see why softwood construction lumber is a different universe than hardwood pricing.
Example 2 — Estimating a Rack Full of 4/4 Oak
Your rack fits 60 linear feet of 4/4 × 8" oak per shelf, across 3 shelves = 180 LF total. At 0.667 BF/LF that's 120 BF of storage capacity per unit.
Example 3 — Converting a Furniture Cut List
A table plan calls for 32 LF of 8/4 × 6" walnut for legs and stretchers. 32 × (2 × 6) ÷ 12 = 32 BF. Add a 15% waste factor → order 37 BF from the dealer.
Example 4 — Reverse: How Much Length in a 100 BF Pack?
A dealer sold you 100 BF of 4/4 × random-width oak, averaging 7" wide. Rough estimate: 100 ÷ ((1 × 7) ÷ 12) = ~171 linear feet — helpful for planning cut layouts.
Frequently Asked Questions
What is the formula for BF to LF?
LF = BF × 12 ÷ (T × W), where T is thickness and W is width in inches. For 4/4 × 6" hardwood: LF = BF × 12 ÷ 6 = BF × 2. So 10 BF = 20 LF.
Is 1 BF always equal to 1 LF?
Only for a specific cross-section: 1×12 nominal (or any board where T × W = 12 sq in, like 2×6 or 3×4). For any other size, BF and LF differ.
Does the converter work with metric?
Board feet is an imperial unit. Convert your metric measurements first: 1 cm = 0.394 in, 1 m = 3.281 ft. Or use the cubic-meter equivalent (1 BF ≈ 0.00236 m³).
Do I use nominal or actual dimensions?
For pricing and buying, use nominal (2×4 stays 2×4). Suppliers charge on nominal even after S4S milling reduces the board to 1.5" × 3.5". Use actual only when your invoice explicitly says so.
How do I handle random-width lumber?
Average the widths, or use our main batch mode to add boards one at a time. Averaging is fine for rough estimates; batch is exact.
Why does my mill invoice differ from this converter?
Mills sometimes round each board to the nearest 0.5" width or apply grade-based deductions. Ask the seller which tally rule they use.
What does "BF vs LF" mean in an invoice?
Some invoices list both: BF for pricing the material, LF for the physical length received. If they disagree, the BF number is what you paid for.