What is a board foot?
A board foot is a unit of lumber volume equal to a board 1 in thick, 12 in wide and 12 in long, which is 144 cubic inches. Hardwood is almost always priced per board foot, and many yards also quote softwood this way.
The formula
Board feet = thickness (in) × width (in) × length (ft) ÷ 12 Total = board feet per piece × number of pieces 1 cubic foot = 12 board feet 1 cubic meter ≈ 423.8 board feetNominal sizes and quarter thickness
Dimensional lumber is named by its nominal size, and board feet are normally calculated from that size. A 2 × 4 counts as 2 in × 4 in even though it measures about 1½ × 3½ in. Rough hardwood thickness is given in quarters of an inch:
| Quarter size | Thickness | Quarter size | Thickness |
|---|---|---|---|
| 4/4 | 1 in | 8/4 | 2 in |
| 5/4 | 1¼ in | 12/4 | 3 in |
| 6/4 | 1½ in | 16/4 | 4 in |
Worked examples
- Ten 2 × 6 boards, 8 ft long: 2 × 6 × 8 ÷ 12 = 8 board feet each, so 80 board feet. At $1.50 per board foot that is $120.
- One 5/4 hardwood board, 8 in wide and 10 ft long: 1.25 × 8 × 10 ÷ 12 = 8.33 board feet.
- Metric: ten pieces of 50 × 150 mm, 2.4 m long: 0.05 × 0.15 × 2.4 = 0.018 m³ each, so 0.18 m³, or about 76 board feet.
Tips
- Add 15–20% for knots, splits and offcuts when buying rough hardwood for furniture.
- Ask whether a price is per board foot, per linear foot or per piece before comparing suppliers.
Frequently asked questions
How do you calculate board feet?
Multiply thickness in inches by width in inches by length in feet, then divide by 12. A 2 × 6 that is 8 ft long is 2 × 6 × 8 ÷ 12 = 8 board feet.
How many board feet are in a 2 × 4 × 8?
2 × 4 × 8 ÷ 12 = 5.33 board feet, using the nominal size.
Do you use nominal or actual size for board feet?
Lumber yards normally use the nominal size for dimensional lumber and the rough (quarter) thickness for hardwood. Ask your supplier if you are unsure.
How do I convert board feet to cubic meters?
Multiply board feet by 0.00236. One cubic meter is about 423.8 board feet.