What is a board foot?
A board foot is a unit of lumber volume used in the United States and Canada: a piece 1 inch thick, 12 inches wide and 12 inches long, or 144 cubic inches. Hardwood is almost always sold by the board foot; framing lumber is usually sold by the piece, but its board footage is useful for comparing prices and for large orders.
Board feet = thickness (in) × width (in) × length (ft) ÷ 12
or thickness (in) × width (in) × length (in) ÷ 144
Worked examples
- A 2 × 6 that is 8 ft long: 2 × 6 × 8 ÷ 12 = 8 board feet. Ten of them are 80 BF; at 4.50 per board foot, 360.00.
- A rough hardwood board 8/4 (2 in) thick, 7 in wide and 9 ft long: 2 × 7 × 9 ÷ 12 = 10.5 BF.
- A 1 × 12 that is 12 ft long: 1 × 12 × 12 ÷ 12 = 12 BF.
Nominal vs actual size
Softwood framing lumber is named by its nominal size, before drying and planing. A 2 × 4 actually measures 1½ × 3½ in. Board feet are traditionally calculated from the nominal size for softwood lumber. Hardwood is sold rough by the board foot using its thickness in quarters of an inch (4/4 = 1 in, 5/4 = 1¼ in, 6/4 = 1½ in, 8/4 = 2 in), and the actual rough width.
| Nominal | Actual (dressed) | BF per linear foot (nominal) |
|---|---|---|
| 1 × 4 | ¾ × 3½ in | 0.333 |
| 1 × 6 | ¾ × 5½ in | 0.5 |
| 2 × 4 | 1½ × 3½ in | 0.667 |
| 2 × 6 | 1½ × 5½ in | 1 |
| 2 × 8 | 1½ × 7¼ in | 1.333 |
| 2 × 10 | 1½ × 9¼ in | 1.667 |
| 2 × 12 | 1½ × 11¼ in | 2 |
| 4 × 4 | 3½ × 3½ in | 1.333 |
Board feet, linear feet and cubic metres
- Linear feet measure length only: ten 8-ft boards are 80 linear feet, whatever their size.
- Board feet include thickness and width, so they measure volume.
- Cubic metres: one board foot is 0.00236 m³, so 1 m³ is about 424 board feet. Lumber outside North America is usually priced per cubic metre.
Buying hardwood
Rough hardwood loses thickness and width when it is planed and jointed, and boards have defects to cut around. Woodworkers commonly buy 20–30% more board feet than the finished parts contain, more for figured wood or projects with many small parts. Measure each rough board's width at its narrowest usable point.
Price per piece vs price per board foot
When a lumberyard prices by the piece, convert to board feet to compare sizes. A 2 × 10 × 12 ft board contains 2 × 10 × 12 ÷ 12 = 20 BF. If it costs 18.00, the price is 0.90 per board foot. A 2 × 6 × 8 ft at 7.20 contains 8 BF, also 0.90 per board foot, so neither is cheaper for the wood itself.
Step by step: buying lumber for a project
- Make a cut list of every part with its finished thickness, width and length.
- Add the planing and cutting allowance to each part.
- Work out the board feet of all parts and add 20–30% for defects when buying rough hardwood.
- Check the yard's stock lengths so the parts fit with little waste.
Common mistakes
- Mixing feet and inches: if the length is in inches, divide by 144, not 12.
- Using actual dimensions when the yard prices on nominal ones (or the other way round). Ask which they use.
- Confusing board feet with linear feet when comparing quotes.
Frequently asked questions
How do I calculate board feet?
Multiply thickness in inches by width in inches by length in feet, then divide by 12. A 2 × 6 × 8 ft board is 2 × 6 × 8 ÷ 12 = 8 board feet.
How many board feet are in a 2×4×8?
Using nominal size, 2 × 4 × 8 ÷ 12 = 5.33 board feet.
What is the difference between board feet and linear feet?
Linear feet measure only length. Board feet measure volume: 1 board foot is 1 in × 12 in × 12 in, or 144 cubic inches.
How many board feet are in a cubic metre?
About 424 board feet, since one board foot is 0.00236 cubic metres.
How do I calculate board feet from inches?
If all three measurements are in inches, multiply thickness × width × length and divide by 144. A board 1 in × 6 in × 96 in is 576 ÷ 144 = 4 board feet.
Sources
- USDA Forest Service, Forest Products Laboratory, Wood Handbook: Wood as an Engineering Material (lumber measurement, board foot).
- American Softwood Lumber Standard, NIST Voluntary Product Standard PS 20 (nominal and dressed sizes).
- National Hardwood Lumber Association (NHLA) rules for the measurement and inspection of hardwood lumber.
Last reviewed 20 October 2026. Results are estimates; see our disclaimer.