Board foot formula
board feet = thickness (in) × width (in) × length (ft) ÷ 12
Example: ten 4/4 boards, 6 inches wide and 8 ft long → 1 × 6 × 8 ÷ 12 = 4 BF each, 40 board feet. If all three dimensions are in inches, divide by 144 instead.
Board feet chart for dimensional lumber
Board feet use the nominal size (a 2×4 counts as 2 × 4 inches even though it measures 1½ × 3½).
| Size | 8 ft | 10 ft | 12 ft | 16 ft | Per linear ft |
|---|---|---|---|---|---|
| 1×4 | 2.67 | 3.33 | 4 | 5.33 | 0.333 |
| 1×6 | 4 | 5 | 6 | 8 | 0.5 |
| 1×8 | 5.33 | 6.67 | 8 | 10.67 | 0.667 |
| 2×4 | 5.33 | 6.67 | 8 | 10.67 | 0.667 |
| 2×6 | 8 | 10 | 12 | 16 | 1 |
| 2×8 | 10.67 | 13.33 | 16 | 21.33 | 1.333 |
| 2×10 | 13.33 | 16.67 | 20 | 26.67 | 1.667 |
| 2×12 | 16 | 20 | 24 | 32 | 2 |
| 4×4 | 10.67 | 13.33 | 16 | 21.33 | 1.333 |
| 6×6 | 24 | 30 | 36 | 48 | 3 |
Hardwood thickness in quarters
Rough hardwood is sold by quarter-inch thickness. Board feet are always figured on this rough (nominal) size:
| Quarter | Rough thickness | Typical surfaced (S2S) | BF per sq ft of face |
|---|---|---|---|
| 4/4 | 1" | 13/16" | 1 |
| 5/4 | 1.25" | 1 1/16" | 1.25 |
| 6/4 | 1.5" | 1 5/16" | 1.5 |
| 8/4 | 2" | 1 3/4" | 2 |
| 12/4 | 3" | 2 3/4" | 3 |
FAQ
How many board feet are in a 2×6×8?
8 board feet: 2 × 6 × 8 ÷ 12.
How do I convert board feet to linear feet?
Linear feet = board feet × 12 ÷ (thickness × width). For 1×6 stock, 40 BF = 80 linear feet.
How much extra lumber should I buy?
For rough hardwood, plan 15–30% over your net cut list for defects, checks, snipe and grain matching; 10% is usually enough for clear, surfaced stock.