How to calculate board feet
To calculate board feet, multiply thickness in inches by width in inches by length in feet and divide by 12. The American Softwood Lumber Standard defines board measure the same way, as nominal thickness in inches times nominal width in feet times length in feet[1].
board feet = T (in) × W (in) × L (in) ÷ 144
Worked examples:
- One 2x4, 8 ft long: 2 × 4 × 8 ÷ 12 = 5.33 board feet.
- A 1x12 shelf, 6 ft: 1 × 12 × 6 ÷ 12 = 6 board feet.
- Ten pieces of 8/4 walnut, 7 in wide, 5 ft long: 2 × 7 × 5 ÷ 12 × 10 = 58.33 board feet.
Board feet for common lumber sizes
Softwood lumber is tallied on its nominal size, so a 2x4 counts as 2 × 4 even though it measures 1-1/2 × 3-1/2 in[1]. The table gives board feet per piece.
| Size | 8 ft | 10 ft | 12 ft | 16 ft |
|---|---|---|---|---|
| 1x4 | 2.67 | 3.33 | 4 | 5.33 |
| 1x6 | 4 | 5 | 6 | 8 |
| 1x8 | 5.33 | 6.67 | 8 | 10.67 |
| 1x12 | 8 | 10 | 12 | 16 |
| 2x4 | 5.33 | 6.67 | 8 | 10.67 |
| 2x6 | 8 | 10 | 12 | 16 |
| 2x8 | 10.67 | 13.33 | 16 | 21.33 |
| 2x10 | 13.33 | 16.67 | 20 | 26.67 |
| 2x12 | 16 | 20 | 24 | 32 |
| 4x4 | 10.67 | 13.33 | 16 | 21.33 |
| 6x6 | 24 | 30 | 36 | 48 |
Hardwood board feet and quarter thickness
Hardwood is measured rough, before planing, with thickness in quarters of an inch: 4/4 is 1 in, 5/4 is 1-1/4 in, 6/4 is 1-1/2 in and 8/4 is 2 in[2]. Enter 5/4 as 1 1/4 or 1.25. Hardwood is sold in random widths, so measure each board; the American Hardwood Export Council describes rounding lengths down to the whole foot and widths to the nearest inch[2].
| Quarters | Rough | Surfaced two sides |
|---|---|---|
| 4/4 | 1 in (25.4 mm) | 13/16 in |
| 5/4 | 1-1/4 in (31.8 mm) | 1-1/16 in |
| 6/4 | 1-1/2 in (38.1 mm) | 1-5/16 in |
| 8/4 | 2 in (50.8 mm) | 1-3/4 in |
The surfaced sizes come from the USDA Wood Handbook[3]. Price is still per board foot of the rough size, so a planed board yields less wood than its tally.
Board feet to cubic metres
One board foot is exactly 0.002359737 m³ (144 in³ at 25.4 mm per inch), so 1 m³ is 423.78 board feet and 1,000 board feet (1 MBF) is 2.36 m³. The standard warns that board feet use nominal sizes while metric volume uses actual sizes, so a converted figure overstates the real wood in dressed softwood[1]. Canadian lumber uses the same dressed sizes, listed in millimetres as 38.1 × 88.9 mm for a 2x4[4].
Pricing by the board foot
Enter the price per board foot (or per m³ in metric) and the calculator totals the list. To compare a price per piece with a price per board foot, divide the piece price by its board feet: an 8 ft 2x6 is 8 board feet, so a piece price of 12 is 1.50 per board foot. For framing lists sold by the piece, the lumber calculator is simpler; for trim and decking priced by length, use the linear feet calculator. Deck projects can start from the deck calculator.
Quick checkA 1x12 one foot long is one board foot. Every other size is a multiple of that board.
Common board foot mistakes
Board foot errors usually come from mixing units or sizes:
- Length in inches divided by 12. With all three dimensions in inches, divide by 144, not 12.
- Actual size for softwood. Softwood is tallied on nominal size: a 2x4 counts as 2 × 4[1].
- Nominal size for hardwood. Hardwood is measured rough, by quarters and measured width[2].
- Board feet vs linear feet. Ten feet of 1x6 is 10 linear feet but 5 board feet.
- Forgetting planing loss. A rough 4/4 board surfaces to 13/16 in[3]; buy enough rough stock for the finished part.
| Part | Pieces | Rough size | Board feet |
|---|---|---|---|
| Sides | 2 | 1 × 12 in × 6 ft | 12 |
| Shelves | 5 | 1 × 11 in × 3 ft | 13.75 |
| Top | 1 | 1 × 12 in × 3-1/2 ft | 3.5 |
| Base | 1 | 2 × 4 in × 3-1/2 ft | 2.33 |
| Total | 9 | 31.58 |
Board feet in a log
Board feet in a standing log are estimated with a log rule rather than measured: the Doyle and International 1/4-inch rules use the small-end diameter inside the bark and the log length[5]. The log board foot calculator applies both and shows how far apart they are on small logs.
Frequently asked questions
How many board feet is a 2x4x8?
2 × 4 × 8 ÷ 12 = 5.33 board feet, using the nominal size as softwood lumber is sold.
What is the formula for board feet?
Thickness in inches × width in inches × length in feet ÷ 12. With all three in inches, divide by 144.
Do you use actual or nominal size for board feet?
Softwood dimension lumber is tallied on nominal size (2x4, not 1-1/2 × 3-1/2). Hardwood uses the rough thickness in quarters and the measured width.
How many board feet are in a cubic metre?
About 423.78. One board foot is 0.002359737 m³.
Can I use this board foot calculator for logs?
No: logs are scaled with a log rule from their diameter and length. Use the log board foot calculator, which applies the Doyle and International 1/4-inch rules.
How much does a board foot of oak weigh?
About 3.7 lb for dry northern red oak at 12% moisture, from its specific gravity of 0.63 in the USDA Wood Handbook (44.1 lb per cubic foot ÷ 12).
How many board feet are in 320 square feet?
Square feet × thickness in inches. For 1 in (4/4) boards, 320 sq ft is 320 board feet; for 2 in stock it is 640.
Is this a lumber board foot calculator for mixed sizes?
Yes. Add a line for each size; the lumber board foot calculator totals every line, in nominal sizes for softwood or rough sizes for hardwood.
How does a board foot price calculator work?
Enter the price per board foot (or per cubic metre) and it multiplies by the total board feet. To compare with a price per piece, divide the piece price by its board feet.
Sources
- Voluntary Product Standard PS 20-25, American Softwood Lumber Standard
- Grading sawn lumber: Measurement
- Wood Handbook (FPL-GTR-282), Chapter 6: Commercial Lumber, Round Timbers, and Ties
- Standard Grading Rules for Canadian Lumber (Para. 820b Standard sizes)
- Log and Tree Scaling Techniques (FNR-191), D. Cassens
- Wood Handbook (FPL-GTR-282), Chapter 5: Mechanical Properties of Wood (Table 5-3b)