How to calculate board feet
A board foot is a volume: 144 cubic inches, the same as a board 1 inch thick, 12 inches wide and 12 inches long.
Board feet = thickness (in) × width (in) × length (ft) ÷ 12
or thickness × width × length (all in inches) ÷ 144
Ten 1 × 6 boards 8 ft long: 1 × 6 × 8 ÷ 12 = 4 BF each, 40 BF total.
Worked example: pricing walnut for a table top
- Measure each board in its rough size. Five boards of 8/4 walnut, each 2 in thick, 7 in wide and 7 ft long.
- Board feet per board. 2 × 7 × 7 ÷ 12 = 8.17 BF.
- All boards. 8.17 × 5 = 40.8 BF.
- Add waste. Allow 25% for knots, checks and offcuts: 40.8 × 1.25 = 51 BF to buy.
- Price it. At $14 per board foot, about $714.
Board feet in common lumber sizes
| Size | 8 ft | 10 ft | 12 ft | 14 ft | 16 ft |
|---|---|---|---|---|---|
| 2x4 | 5.33 | 6.67 | 8 | 9.33 | 10.67 |
| 2x6 | 8 | 10 | 12 | 14 | 16 |
| 2x8 | 10.67 | 13.33 | 16 | 18.67 | 21.33 |
| 2x10 | 13.33 | 16.67 | 20 | 23.33 | 26.67 |
| 2x12 | 16 | 20 | 24 | 28 | 32 |
Figures use the nominal size, the way lumberyards count board feet. For the real dimensions of each size, see the lumber dimensions chart.
Board feet vs linear feet
A linear foot is just length, whatever the size of the board. A board foot is volume. Construction lumber like 2x4s is usually priced per piece or per linear foot, while hardwood is priced per board foot. To convert: board feet = linear feet × thickness (in) × width (in) ÷ 12. Twenty linear feet of 1x6 is 20 × 1 × 6 ÷ 12 = 10 board feet.
Hardwood thickness: the quarter system
| Quarters | Rough thickness | Typical surfaced (S2S) |
|---|---|---|
| 4/4 | 1" | 13/16" |
| 5/4 | 1-1/4" | 1-1/16" |
| 6/4 | 1-1/2" | 1-5/16" |
| 8/4 | 2" | 1-3/4" |
| 12/4 | 3" | 2-3/4" |
Pricing logs instead of boards? The log weight calculator also estimates Doyle board feet.
Frequently asked questions
How many board feet is a 2x4x8?
5.33 board feet using nominal size (2 × 4 × 8 ÷ 12). Construction lumber is usually sold per piece or linear foot, not by the board foot.
How do I convert linear feet to board feet?
Multiply linear feet by thickness and width in inches, then divide by 12.
Is a board foot the same as a square foot?
Only for 1-inch-thick material. A board foot includes thickness; a square foot does not.