How to calculate board feet
A board foot represents the volume of a board 1 inch thick, 12 inches wide, and 12 inches long. Multiply dimensions in inches and feet, then divide by 12.
Six 2 × 8 boards at 10 ft
Using 2-inch thickness and 8-inch width
The board-foot formula
If length is measured in inches, multiply all three dimensions in inches and divide by 144.
Nominal versus actual dimensions
Board-foot pricing for rough hardwood commonly uses nominal thickness and measured width and length according to the seller’s rules. Surfaced construction lumber is often named by a nominal size that is larger than its actual dressed dimensions. Ask the supplier which dimensions and rounding method appear on the tally.
Quick examples
| Piece | Formula | Board feet |
|---|---|---|
| 1 × 6 × 8 ft | 1 × 6 × 8 ÷ 12 | 4.0 |
| 2 × 10 × 12 ft | 2 × 10 × 12 ÷ 12 | 20.0 |
| 4/4 × 9 × 7 ft | 1 × 9 × 7 ÷ 12 | 5.25 |
| 8/4 × 7 × 6 ft | 2 × 7 × 6 ÷ 12 | 7.0 |
Build a useful lumber tally
- Group boards by thickness.
- Record width and length using the supplier’s measurement convention.
- Calculate each piece or group of identical pieces.
- Add the board feet across the order.
- Add a separate waste allowance instead of quietly changing dimensions.
- Multiply the final tally by price per board foot for a material estimate.
Frequently asked questions
Is one board foot the same as one square foot?
No. A board foot includes a one-inch thickness. Square feet measure surface area only.
What does 4/4 lumber mean?
It is a rough-thickness designation expressed in quarter inches. Four-quarter is nominally one inch thick; eight-quarter is nominally two inches before surfacing.
Should I use actual size for a 2×4?
For project volume, actual dimensions may be useful. For purchasing, use the measurement and pricing convention stated by the lumber seller.