Board Feet ↔ Linear Feet Converter
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What is a Board Foot?
A board foot (BF) is a standard unit of volume for lumber in the United States, equal to 144 cubic inches (a 12" × 12" × 1" piece). Unlike linear feet which measure only length, board feet account for thickness, width, and length — making it essential for pricing hardwood lumber.
Formula: Board Feet = (Thickness" × Width" × Length in feet) ÷ 12
Board Feet Formula & How It Works
The board-foot formula accounts for all three dimensions of a piece of lumber:
Linear Feet = (Board Feet × 12) ÷ (Thickness" × Width")
Example: You have 30 board feet of 4/4 (1-inch thick) × 5-inch-wide oak. How many linear feet is that?
Linear Feet = (30 × 12) ÷ (1 × 5) = 360 ÷ 5 = 72 linear feet
At a lumberyard, you might buy those 72 LF as four 6-foot boards, ten 8-foot boards, or any combination — the total board footage is the same. The calculator above lets you work backward from BF to LF or forward from dimensions to BF.
Hardwood Thickness: The Quarter System Explained
Hardwood lumberyards sell lumber in "quarter" increments (4/4, 5/4, 6/4, 8/4…). Each quarter equals ¼ inch of rough-sawn thickness. After surfacing (planing smooth on 2 sides, called S2S), the actual thickness is slightly less.
| Quarters | Rough In | Surfaced (S2S) | Common Uses |
|---|---|---|---|
| 4/4 | 1" | 13/16" | Most common; furniture, cabinets |
| 5/4 | 1¼" | 1 1/16" | Decking, stair treads |
| 6/4 | 1½" | 1 5/16" | Thick table tops |
| 8/4 | 2" | 1¾" | Heavy furniture, turning blanks |
| 10/4 | 2½" | 2¼" | Large slabs, workbenches |
| 12/4 | 3" | 2¾" | Extra thick slabs, specialty |
Lumber Species Reference — Hardwood vs. Softwood Pricing
How a species is sold determines whether you need to think in board feet or linear feet. Hardwoods are priced by volume (BF); softwood dimensional lumber is priced by the piece or linear foot.
| Species | Thickness | Common Widths | LF per 10 BF (3" wide) | LF per 10 BF (6" wide) | Sold By |
|---|---|---|---|---|---|
| Red Oak | 4/4 (1") | 3", 4", 5", 6", 8" | 120 | 60 | Board foot |
| Hard Maple | 4/4 (1") | 3"–10" random | 120 | 60 | Board foot |
| Walnut | 4/4–8/4 | 4"–12" random | 120 | 60 | Board foot |
| Douglas Fir (dimensional) | 2×4, 2×6, 2×8 | 3.5", 5.5", 7.25" | — | — | Linear foot / piece |
| Southern Yellow Pine | 2×4, 2×6, 2×10 | 3.5", 5.5", 9.25" | — | — | Linear foot / piece |
| Cedar (Western Red) | 1×4, 1×6, 2×4 | 3.5", 5.5" | — | — | Linear foot / piece |
* LF per 10 BF calculated at 4/4 (1") thickness. Values for hardwood species only.
How to Order Hardwood Lumber by the Board Foot
- 1Build a cut list in linear feet
List every part of your project (legs, aprons, panels) with its thickness, width, and length. Calculate linear feet for each species and size group.
- 2Convert to board feet
Group parts by thickness and width. Use the formula BF = (T″ × W″ × LF) ÷ 12 for each group, then sum across groups.
- 3Add 20–25% waste
Hardwood comes with knots, checks, and wane you'll cut around. Furniture-grade projects need at least 20% buffer; character-grade material may need 30%.
- 4Ask for FAS or #1 Common grade
FAS (Firsts and Seconds) yields 83⅓%+ clear cuttings per board — ideal for large flat surfaces. #1 Common yields 66⅔%+ and is more economical for smaller parts.
- 5Order in the same log-run if possible
Color and grain vary between mill runs. Order all the board feet for a project at once, and keep off-cuts for repairs.
Related Calculators
Know your linear feet? Now calculate total material cost using $/LF benchmarks.
Convert square footage to linear feet for flooring or hardwood plank orders.
Measure cabinet runs in linear feet — many cabinet wood orders start with board feet.
Need flooring coverage, LTL freight, or price-per-linear-foot calculations?
Use the Full Linear Feet Calculator →