What is a Board Foot? Definition, Uses & How It's Measured
Last Updated: 2025-12-28
Learn what a board foot is: 144 cubic inches (12×12×1 inch). Used in lumber pricing, woodworking, and spray foam insulation. Free calculator included.
A board foot (BF) is a unit of lumber volume, equal to 144 cubic inches.
1 BF = 12" × 12" × 1" = 144 cubic inches
A simple way to remember: 1 foot × 1 foot × 1 inch.
How to calculate board feet (quick steps)
If you know the board’s actual thickness and width, board feet is just volume math. For instant results, use the board foot calculator .
Board Feet = (Thickness(in) × Width(in) × Length(in)) ÷ 144
Tip: If you measured length in feet, convert first: Length(in) = Length(ft) × 12.
- 1
Measure actual thickness and width (inches)
Use actual size (for example, a “2×4” is often 1.5" × 3.5").
- 2
Convert length to inches
If length is in feet, multiply by 12 (8 ft → 96 in).
- 3
Multiply to get cubic inches
Thickness × width × length(in) gives volume in cubic inches.
- 4
Divide by 144 (and multiply by quantity)
Divide by 144 to get board feet. If you have multiple boards, multiply by quantity.
Micro examples (worked)
- 1" × 6" × 8' → (1 × 6 × 96) ÷ 144 = 4 BF
- 2" × 4" × 10' → (2 × 4 × 120) ÷ 144 = 6.67 BF
Prefer a cleaner breakdown? See the board foot formula page.
Visual explanation (12×12×1)
Think of 1 board foot as a flat block that is 12 inches wide, 12 inches long, and 1 inch thick. If thickness changes, board feet changes too.
Why board feet is used
Board feet is common in the lumber industry, especially for hardwood, because it includes thickness. It makes pricing fair when boards have different sizes.
- Compares boards with different thickness fairly
- Matches how lumber is often priced ($/BF)
- Avoids confusion when linear feet pricing hides thickness
Common applications
Lumber industry (hardwood sales)
Hardwood boards come in many widths. Board feet helps sellers and buyers price wood consistently.
Woodworking projects
Board feet helps you estimate how much material you need before you buy lumber.
Logs and large quantities (MBF)
For big trades, you may see MBF (thousand board feet). 1 MBF = 1,000 BF.
Spray foam insulation (industry usage)
In spray foam, “board foot” measures coverage volume: 12" × 12" × 1" of applied foam. Contractors use it to estimate material and pricing. The definition is the same 144 cubic inches.
Board foot vs other units
Linear foot is length. Square foot is area. Board foot is volume.
| Unit | What it measures | What it ignores |
|---|---|---|
| Board foot (BF) | Volume | — |
| Linear foot (LF) | Length | Width + thickness |
| Square foot (SF) | Area | Thickness |
Common confusion: nominal vs actual size
Always use actual size when you calculate volume. Dimensional lumber labels like 2×4 are nominal names. The real measured size is smaller after drying and planing.
Quick example
A 2×4 is usually 1.5" × 3.5" (actual). Using nominal size can overestimate board feet.
Try the calculator
FAQ
Related links
Board Foot Calculator
Calculate board feet instantly.
Learn the Board Foot Formula
See the formula and worked examples.
Log Board Foot Calculator
Estimate board feet from logs.
Board Feet to Square Feet
Convert board feet to square feet.
Board Feet to Linear Feet
Convert based on board size.
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