Lumber Board Feet Calculator
Lumber is priced and sold by the board foot — a unit of volume measurement used in the lumber industry. Understanding board feet helps you compare prices and buy the right amount for your project. Our lumber calculator converts any size and quantity of wood into board feet.
What Is a Board Foot?
A board foot (abbreviated BDFT, BF, or FBM) is a volume measurement:
It is a volume measurement — 1/12 of a cubic foot, or 144 cubic inches.
The Board Foot Formula
Where T = thickness in inches, W = width in inches, L = length in feet, Qty = number of pieces.
Nominal vs. Actual Sizes
Important: lumber is sold by nominal size but actually measures actual size:
- 2×4 → actual: 1.5" × 3.5"
- 2×6 → actual: 1.5" × 5.5"
- 2×8 → actual: 1.5" × 7.25"
- 2×10 → actual: 1.5" × 9.25"
- 2×12 → actual: 1.5" × 11.25"
- 4×4 → actual: 3.5" × 3.5"
- 1×4 → actual: 0.75" × 3.5"
Board foot calculations use nominal sizes for pricing — that is how the lumber industry works. For actual volume, use actual dimensions.
Example Calculation
10 pieces of 2×4 × 8 ft:
- Board feet per piece: (2 × 4 × 8) ÷ 12 = 5.33 BF
- Total: 5.33 × 10 = 53.33 board feet
- At $4/BF: 53.33 × $4 = $213.33
Common Lumber Species
- Pine / Fir (SPF) — construction framing, cheapest
- Douglas Fir — strong, structural beams, deck framing
- Cedar — rot-resistant, decks, siding, outdoor furniture
- Redwood — beautiful, durable, premium price
- Oak (red / white) — furniture, flooring, cabinetry
- Maple — hardwood flooring, cabinets, furniture
- Poplar — paint-grade woodwork, inexpensive hardwood
- Walnut — premium furniture, dark rich color
FAQ
How many board feet are in a 2x4x8?
5.33 board feet. (2 × 4 × 8) ÷ 12 = 5.33 BF.
Why is it called a 2x4 if it is only 1.5x3.5?
The nominal size refers to the rough-cut dimension before planing and drying. The actual size is smaller after milling.
What does S4S mean?
Surfaced 4 sides — all four faces planed smooth. Most construction lumber is S4S.