What Is a Board Foot?
A board foot is a unit of lumber volume equal to a piece measuring 1 inch thick × 12 inches wide × 12 inches long — or any combination that equals the same volume. It's the standard unit used by lumber yards, sawmills, and hardwood dealers across North America. Use this free tool to calculate board feet for any board size before you order.
Board Foot Formula
Where thickness and width are in inches, and length is in feet.
Example Calculation
A board that is 1.5" thick × 5.5" wide × 8 feet long:
Common Lumber Sizes in Board Feet
| Nominal Size | Actual Size | BF per 8ft board | BF per 12ft board |
|---|---|---|---|
| 1×4 | ¾" × 3½" | 1.75 | 2.63 |
| 1×6 | ¾" × 5½" | 2.75 | 4.13 |
| 2×4 | 1½" × 3½" | 3.5 | 5.25 |
| 2×6 | 1½" × 5½" | 5.5 | 8.25 |
| 2×8 | 1½" × 7¼" | 7.25 | 10.88 |
| 2×10 | 1½" × 9¼" | 9.25 | 13.88 |
| 4×4 | 3½" × 3½" | 8.17 | 12.25 |
When Do You Need Board Feet?
- Ordering hardwood at a lumber yard (hardwood is sold by the board foot)
- Estimating lumber costs for furniture or cabinet making
- Calculating wood for flooring, decking, or siding projects
- Comparing prices between different board sizes
Frequently Asked Questions
What is a board foot of lumber?+
A board foot is a unit of lumber volume equal to 1 inch thick × 12 inches wide × 12 inches long. It equals 144 cubic inches. This is the standard unit used by hardwood dealers and sawmills across North America.
How do you calculate board feet?+
Use the formula: Board Feet = (Thickness in inches × Width in inches × Length in feet) ÷ 12. For example, a 2×6 board that is 10 feet long equals (2 × 6 × 10) ÷ 12 = 10 board feet.
Is framing lumber sold by the board foot?+
No. Framing lumber (2×4, 2×6, etc.) is sold by the linear foot or per board at home improvement stores. Board feet are primarily used for hardwood lumber at specialty dealers.
How many board feet in a 2x4x8?+
A standard 2×4 that is 8 feet long contains (1.5 × 3.5 × 8) ÷ 12 = 3.5 board feet, using actual dimensions. Using nominal dimensions (2 × 4 × 8) ÷ 12 = 5.33 board feet.