What is a board foot?
A board foot is a unit of lumber volume used in the United States and Canada, mainly for hardwood and specialty lumber. One board foot equals a piece of wood 1 inch thick, 12 inches wide and 12 inches long, which is 144 cubic inches or 1/12 of a cubic foot.
Hardwood yards often price by the board foot because boards come in many thicknesses, widths and lengths. Pricing by volume lets you compare a thin wide board and a thick narrow board fairly.
How to calculate board feet by hand
- Measure thickness and width in inches.
- Measure length in feet (divide inches by 12 if needed).
- Multiply thickness ร width ร length.
- Divide by 12.
- Multiply by the number of boards.
If the length is in inches, use thickness ร width ร length in inches รท 144 instead. This calculator does the conversion when you pick inches.
Nominal vs actual lumber sizes
Lumber is named by its nominal size, but the finished board is smaller after drying and planing. A 2x4 is really about 1.5 in by 3.5 in. Board feet are normally figured on nominal dimensions for dimensional lumber, which is how most sellers price it. Rough-sawn hardwood is usually sold by its actual rough thickness, quoted in quarters, such as 4/4 (1 inch) or 8/4 (2 inches).
| Nominal size | Typical actual size | Board feet per linear foot (nominal) |
|---|---|---|
| 1x4 | 3/4 ร 3-1/2 in | 0.33 |
| 1x6 | 3/4 ร 5-1/2 in | 0.50 |
| 2x4 | 1-1/2 ร 3-1/2 in | 0.67 |
| 2x6 | 1-1/2 ร 5-1/2 in | 1.00 |
| 2x8 | 1-1/2 ร 7-1/4 in | 1.33 |
| 2x10 | 1-1/2 ร 9-1/4 in | 1.67 |
| 2x12 | 1-1/2 ร 11-1/4 in | 2.00 |
| 4x4 | 3-1/2 ร 3-1/2 in | 1.33 |
How to use this calculator for a project
- Mixed boards: run the calculator once for each size and add the totals.
- Plan for waste: add about 10% to 20% for knots, defects, and saw cuts, more for furniture-grade work where you need clear wood.
- Check the price basis: some yards sell softwood by the piece or linear foot and hardwood by the board foot. Make sure you compare like with like.
- Ask about thickness: if a seller quotes surfaced thickness, ask whether the price is per rough or per finished board foot.
Common mistakes
- Using actual 1.5 ร 3.5 instead of nominal 2 ร 4 when the seller prices on nominal size.
- Entering length in inches while the unit is set to feet.
- Forgetting that board feet measure volume, so doubling the thickness doubles the board feet.
- Not rounding up to whole boards when you shop. Boards come in set lengths such as 8, 10 and 12 feet.
Board feet, cubic feet and square feet
One board foot is 1/12 of a cubic foot, so 12 board feet make one cubic foot of wood. Square feet measure only surface area, which is what you want for flooring or paneling. If you are covering a floor rather than building with solid lumber, use a square feet calculator instead.