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Board Foot Calculator: Lumber Volume and Price
Convert lumber dimensions into board feet, the unit hardwood and rough lumber are sold by. Enter thickness, width, length and quantity to get total board feet and cost.
What is a board foot?
A board foot is a volume of wood 12 in long, 12 in wide and 1 in thick: 144 cubic inches. A 1 × 12 board 1 ft long is one board foot, and so is a 2 × 6 that is 1 ft long. With the length in feet:
board feet = thickness (in) × width (in) × length (ft) ÷ 12
Worked examples
- Ten 1 × 6 boards, 8 ft long: 1 × 6 × 8 ÷ 12 = 4 BF each, 40 BF in total. At $6 per BF that is $240.
- One 8/4 walnut board, 7 in wide, 6 ft long: 2 × 7 × 6 ÷ 12 = 7 BF. At $14 per BF it costs $98.
- A 4 × 4 post, 10 ft long: 4 × 4 × 10 ÷ 12 = 13.3 BF.
Nominal vs actual size
Board feet are calculated from nominal (rough) dimensions. A 2 × 4 from a home center actually measures 1½ × 3½ in, but it is still sold and counted as 2 × 4. Hardwood thickness is given in quarters of an inch, measured rough before planing:
| Quarter size | Rough thickness | Typical surfaced (S2S) |
|---|---|---|
| 4/4 | 1 in | ¾ to 13/16 in |
| 5/4 | 1¼ in | 1 to 1 1/16 in |
| 6/4 | 1½ in | 1¼ to 1 5/16 in |
| 8/4 | 2 in | 1¾ in |
| 12/4 | 3 in | 2¾ in |
Enter the nominal thickness (1 for 4/4, 2 for 8/4) to match how lumberyards price it.
Buying tips
- Add 15 to 30% for waste when buying rough hardwood: defects, knots, checks at board ends and planing all cost yield.
- Random-width hardwood is sold by the total board feet in the pile you pick, so measure each board's width and add them up.
- Softwood construction lumber is usually priced per piece or per linear foot instead. The calculator shows the linear-foot equivalent.
Building a deck? The deck calculator counts boards and joists for you.
Frequently asked questions
How do you calculate board feet?
Multiply thickness (in) × width (in) × length (ft) and divide by 12. A 1 × 6 board 8 ft long is 4 board feet.
How many board feet in a 2x4x8?
2 × 4 × 8 ÷ 12 = 5.33 board feet, using nominal dimensions.
Is a board foot the same as a linear foot?
No. A linear foot measures length only. A board foot is a volume: 144 cubic inches. A 1 × 12 board 1 ft long is one board foot and one linear foot; a 1 × 6 needs 2 linear feet to make one board foot.