What to measure
How to use the board foot calculator
Enter the thickness and width in inches and the length in feet, then the number of boards. Add the price per board foot from the lumberyard’s list to see the cost.
The formula
Board feet = thickness (in) × width (in) × length (ft) ÷ 12
If you measure the length in inches too, divide by 144 instead.
Worked example: ten 4/4 oak boards, 6 in × 8 ft
- One board: 1 × 6 × 8 ÷ 12 = 4 board feet
- Ten boards: 40 board feet (80 linear feet)
- At $5.50 per board foot: $220
Common sizes
| Board | Board feet per foot of length |
|---|---|
| 4/4 × 6 in | 0.5 |
| 4/4 × 8 in | 0.67 |
| 8/4 × 6 in | 1 |
| 2×4 (nominal) | 0.67 |
| 2×6 (nominal) | 1 |
Buying for a project? Add 15–20% for defects and offcuts, and more for figured or knotty stock.
Board feet in common lumber
Nominal dimensions, one board.
| Board | 8 ft | 10 ft | 12 ft |
|---|---|---|---|
| 1×6 | 4 | 5 | 6 |
| 1×8 | 5.33 | 6.67 | 8 |
| 2×4 | 5.33 | 6.67 | 8 |
| 2×6 | 8 | 10 | 12 |
| 2×8 | 10.67 | 13.33 | 16 |
| 2×10 | 13.33 | 16.67 | 20 |
| 2×12 | 16 | 20 | 24 |
| 4×4 | 10.67 | 13.33 | 16 |
Common mistakes
- Using planed sizes. Lumber is priced by its nominal or rough size, not the smaller size after planing.
- Entering the length in inches without changing the unit. With length in inches, divide by 144 instead of 12, or switch the field to inches.
- Reading 5/4 as 1 inch. Each quarter is ¼ in, so 5/4 is 1¼ in and has 25% more board feet than 4/4.
- Buying exactly what the plan shows. Defects, checks and offcuts take their share. Add the extra before you order.
Frequently asked questions
What is a board foot?
A volume of wood equal to 144 cubic inches, the same as a board 1 inch thick, 12 inches wide and 1 foot long. That's 1/12 of a cubic foot.
What does 4/4, 5/4 or 8/4 mean?
Hardwood thickness in quarters of an inch, measured rough-sawn. 4/4 ("four quarter") is 1 inch, 5/4 is 1¼ inches, 6/4 is 1½, 8/4 is 2 inches. Use those rough figures for board feet even though boards are thinner after planing.
Do I use nominal or actual dimensions?
Use the size the lumberyard prices by, which is the rough or nominal size. A 2×4 is priced as 2 × 4 inches even though it measures 1½ × 3½. Hardwoods are priced by rough thickness (the quarters) and the actual width.
How many board feet are in a 2x4x8?
2 × 4 × 8 ÷ 12 = 5.33 board feet, using nominal dimensions.
How many board feet are in a 4x4x8?
10.67 board feet, using nominal dimensions (4 × 4 × 8 ÷ 12).
How do I convert board feet to linear feet?
Divide the board feet by thickness × width ÷ 12, with sizes in inches. 100 board feet of 4/4 × 6 in lumber is 200 linear feet.
How many board feet are in a cubic foot?
12. A board foot is 144 cubic inches, and a cubic foot is 1,728.
How many board feet are in a 2x6x10?
10 board feet, using nominal dimensions (2 × 6 × 10 ÷ 12). A 2x12x16 is 32 board feet.
Sources
Formulas and defaults last reviewed October 30, 2026. How we check our math.