Explanation
Lumber board-foot volume
A board foot measures lumber volume: one inch thick by twelve inches wide by one foot long. It is a volume convention, not a count of boards or a structural rating.
Measure the actual board
Enter actual measured thickness and width in inches, length in feet, and the whole-board quantity. A nominal 2×6 typically measures 1.5 in × 5.5 in. If purchasing by a supplier’s nominal tally, confirm their measurement convention.
B = T × W × L × n ÷ 12
| B | Board feet |
|---|---|
| T | Thickness |
| W | Width |
| L | Length |
| n | Boards |
One 1 × 12 board, 8 ft long
| Thickness | 1 |
|---|---|
| Width | 12 |
| Length | 8 |
| Boards | 1 |
| Result | 8 board ft |
1 in × 12 in × 8 ft ÷ 12 = 8 board ft per board. × 1 boards = 8 board ft.
Four actual-size 2 × 4s
| Thickness | 1.5 |
|---|---|
| Width | 3.5 |
| Length | 8 |
| Boards | 4 |
| Result | 14 board ft |
1.5 in × 3.5 in × 8 ft ÷ 12 = 3.5 board ft per board. × 4 boards = 14 board ft.
Two 2 × 6 boards, 10 ft long
| Thickness | 2 |
|---|---|
| Width | 6 |
| Length | 10 |
| Boards | 2 |
| Result | 20 board ft |
2 in × 6 in × 10 ft ÷ 12 = 10 board ft per board. × 2 boards = 20 board ft.
Diagram of this result
The board is drawn with its thickness and width enlarged so the labels stay readable. One board foot is 144 cubic inches: 1 in × 12 in × 1 ft.
Thickness, width, length, board feet per board, board count and total are stated as numbers in the diagram.
Common mistakes
A nominal two-by-four usually does not measure two inches by four inches. Using nominal dimensions in an actual-volume estimate overstates the wood volume.
Assumptions and limits
Positive dimensions up to one million; integer quantity 1–100. Decimal board-foot volume is not rounded to a purchasing count. Species, grade, moisture, strength and waste allowances are outside scope. Material estimates only; verify measurements, product guidance and site requirements before ordering.
Is one board foot one square foot?
No. A board foot is a volume of 144 cubic inches. Square feet measure area and require a thickness to become volume.
Method and references
Thickness and width in inches times length in feet gives inch-inch-feet; dividing by 12 converts to board feet of 144 cubic inches each. Nominal-to-actual sizes vary by supplier and species.