What Is a Board Foot?
A board foot is 144 cubic inches of wood — the standard volumetric unit for pricing lumber in North America. Here's the full picture: what it is, why it exists, and how it differs from linear feet and square feet.
The Board Foot, Precisely
A board foot (BF, bd. ft., or FBM) is 144 cubic inches of wood. That's the exact volume of a piece that measures:
- 1 inch thick × 12 inches wide × 12 inches long, or
- 1 inch thick × 6 inches wide × 24 inches long, or
- 2 inches thick × 6 inches wide × 12 inches long, or
- Any combination where T × W × L (all in inches) = 144.
The formulas most people memorize are:
BF = (T × W × L_ft) ÷ 12
(with T and W in inches, L in feet), or the all-inches variant:
BF = (T × W × L_in) ÷ 144
Both give the same answer — the divisor changes because you're converting units of length differently.
BF vs LF vs sq ft — All Three, Compared
| Unit | Measures | Formula | Common Use |
|---|---|---|---|
| Linear foot (LF) | Length only | L in feet | Trim, moulding, piece-sold 2× lumber |
| Square foot (sq ft) | Area | L × W | Plywood, MDF, flooring, drywall |
| Board foot (BF) | Volume | (T × W × L) ÷ 12 | Rough hardwood, exotics, packs |
A single 12-foot 1×6 board is 12 linear feet, 6 square feet of surface area, and 6 board feet of volume. All three numbers describe the same physical stick — they just measure different aspects.
Why Hardwood Is Priced by BF (and Softwood Isn't)
Construction softwood — Douglas fir, spruce, pine — comes out of the mill in fixed nominal dimensions: 2×4, 2×6, 2×8. Because every piece of a given size is (roughly) identical, it's fair to price by the piece or by the linear foot.
Hardwood — walnut, oak, cherry, maple — is different. Sawyers cut hardwood logs in random widths, and boards come off the mill in a range of thicknesses (4/4, 5/4, 6/4, 8/4). Charging by the linear foot would penalize the buyer who receives narrow boards and reward one who happens to get 14" widths. Pricing by volume — board feet — is neutral: you pay for the wood you actually receive.
The system dates to the 1800s
Board-foot pricing evolved through the 19th century as US and Canadian hardwood mills standardized their trade. By 1898 the NHLA (National Hardwood Lumber Association) had codified grading rules that still reference board feet today.
Where Board Feet Is Used (and Where It Isn't)
- United States, Canada — universal for hardwood, common for premium softwood.
- Philippines — board feet is the standard hardwood unit despite Metric elsewhere in commerce.
- Pakistan, India — used in the timber trade for imported hardwoods and traditional local species (deodar, teak, shisham).
- UK, Australia, most of Europe — metric cubic meters (m³) dominate. Board feet is rare.
- Japan, China — mostly cubic meters, with piece-count for standard sizes.
If you're buying imported wood, always confirm the unit: 1 m³ ≈ 424 BF, so a "small" 5 m³ shipment is actually ~2,100 BF.
Common Misconceptions
"A board foot is a foot of board"
No. A board foot is a volume, not a length. A 12-foot 1×6 is 12 linear feet but only 6 board feet — because the volume is (1×6×12)÷12 = 6.
"I should use the actual dried size (1.5 × 3.5) for a 2×4"
For pricing, no. Suppliers charge on nominal size. Use 2 × 4 for the BF math even though the physical board is 1.5 × 3.5.
"BF and MBF are different units"
They're the same unit at different scales. 1 MBF = 1,000 BF. Use MBF for wholesale, BF for retail.
"144 cubic inches is arbitrary"
It's exactly the volume of a 1" × 12" × 12" board — the imperial version of a "square meter of one-inch-thick wood." Not arbitrary; historically deliberate.
Frequently Asked Questions
What does BF stand for in lumber?
BF = board foot. It's the standard imperial volumetric unit for lumber: 144 cubic inches per BF.
What's the difference between BF and bd. ft.?
Nothing — they're the same abbreviation. "BF" is more common in North America, "bd. ft." on older invoices and forestry publications.
Is BF the same as FBM?
Yes. FBM = "feet board measure" — an older, less common notation for board feet. Same unit, same math.
How many BF is a 2×4 × 8 ft?
(2 × 4 × 8) ÷ 12 = 5.33 BF.
How many BF is 100 board feet?
100 board feet is 100 BF. If you meant 100 pieces of 1×12 × 1', that's exactly 100 BF too (by definition).
How is BF measured?
Calculated, not directly measured. You measure T, W, L with a tape and apply the formula. The unit is a volume; the measurement uses ordinary length instruments.
What is 1 BF in cubic feet?
1 BF = 144 in³ ÷ 1,728 in³/ft³ = 0.0833 ft³. Or: 12 BF = 1 ft³.
What is 1 BF in cubic meters?
1 BF ≈ 0.00236 m³. Inversely, 1 m³ ≈ 424 BF.
Do metric countries use board feet?
Rarely in domestic trade, sometimes for US/Canadian imports. Most metric-country invoices use m³ or piece-count.
Related Tools
- Main Board Feet Calculator — Lumber, log, batch modes
- BF ↔ LF Converter
- MBF Calculator
- Board Foot Chart