Board Foot Calculator
Board feet = thickness (in) × width (in) × length (ft) ÷ 12. An 8 ft 2×4 holds 2 × 4 × 8 ÷ 12 = 5.33 bf, counted on its nominal size as lumberyards do. Softwood is billed on its nominal size (a 2×4, not 1 1/2 × 3 1/2 in); hardwood on thickness in quarters, 4/4 = 1 in.
Board feet
5.33 bf
0.44 ft³ of nominal lumber
- Per piece
- 5.33 bf
- Volume
- 0.44 ft³ · 0.013 m³
- Linear feet
- 8 ft
Worked examples
One 2×4, 8 ft long
- 2 × 4 × 8 = 64
- 64 ÷ 12 = 5.33 bf
Result: 5.33 board feet.
Checked by the automated test “board foot — 2×4×8 = 5.33 bf; 2×4×10 = 6.67 bf; 2×4×16 = 10.67 bf (Briggs ch. 4)”.
20 boards of 1×6, 8 ft long, at $4.50 per board foot
- 1 × 6 × 8 ÷ 12 = 4 bf per board
- 4 × 20 = 80 bf; 80 × $4.50 = $360
Result: 80 board feet, $360.
Checked by the automated test “board foot — quantity and price: 20 boards of 1×6 × 8 ft = 80 bf; at $4.50/bf = $360”.
How it works
Board feet = thickness (in) × width (in) × length (ft) ÷ 12
Same thing with the length in inches: thickness × width × length (in) ÷ 144
Total = board feet per piece × number of pieces · 1 bf = 144 in³ = 0.00236 m³
Assumptions
- One board foot is 12 in × 12 in × 1 in, or 144 cubic inches (UW-Madison Extension).
- Softwood lumber is tallied on its nominal size: a 2×4 counts as 2 × 4 in even though it measures 1 1/2 × 3 1/2 in (Briggs, University of Washington).
- Hardwood is sold by nominal thickness in quarters (4/4 = 1 in, 8/4 = 2 in); mills round the surface measure, so a mill tally can differ slightly from this exact figure.
Reference table
| Size (in) | 8 ft | 10 ft | 12 ft |
|---|---|---|---|
| 1×4 | 2.67 | 3.33 | 4 |
| 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 |
| 6×6 | 24 | 30 | 36 |
Using the result
- Comparing quotes. Board feet put a price per piece and a price per board foot on the same footing: divide the piece price by its board feet.
- Hardwood. Enter the nominal thickness in quarters (4/4 = 1 in) and the width you measure; Briggs notes that mills round each board’s surface measure to a whole number.
- Mixed orders. Run each size separately and add the board feet.
Common mistakes
- Using actual sizes for softwood billed on nominal A 2×4 measured at 1 1/2 × 3 1/2 in gives 3.5 bf per 8 ft instead of 5.33: 34 % short of what the yard bills.
- Length in inches with the ÷ 12 formula 96 in × 2 × 4 ÷ 12 gives 64, twelve times too much. With inches, divide by 144; with feet, by 12.
- Applying it to logs A round log is not a board: UW-Madison Extension notes that log rules (tables) are needed because saw kerf and slabs are lost.
Frequently asked questions
How do you figure out board feet?
Multiply thickness by width in inches and length in feet, then divide by 12. A 10 ft 2×6 is 2 × 6 × 10 ÷ 12 = 10 bf (UW-Madison Extension).
How do you measure lumber in board feet?
For softwood, read the nominal size on the tag (2×4, 1×6) and the length. For a stack of boards of one length, measure its height and width in inches: a 36 × 60 in stack of 8 ft boards is 36 × 60 × 8 ÷ 12 = 1,440 bf.
How many board feet are in a 2x4x8?
5.33 board feet: 2 × 4 × 8 ÷ 12. Briggs (University of Washington) gives the same 5.33 BF.
How many board feet are in a 2x4x10?
6.67 board feet: 2 × 4 × 10 ÷ 12.
Sources
Formula, examples and sources checked on by the Yardstick Math team. How we check our formulas.
- What Is A Board Foot? (Forest and Wildlife Ecology No. 42) — University of Wisconsin–Madison Extension, accessed
- Forest Products Measurements and Conversion Factors, Chapter 4: Lumber (D. Briggs) — University of Washington, Rural Technology Initiative, accessed
- Handbook 44, Appendix C – General Tables of Units of Measurement (1 in = 2.54 cm) — NIST, accessed