How to use the board foot calculator
Choose the thickness, enter the width and length of a board and how many you have. Hardwood dealers price almost everything per board foot, so this is the number to bring to the lumberyard, or to check against an invoice. Enter the price per board foot to see the total and the cost of each board.
Boards of different sizes? Run each size separately and add the totals. Hardwood boards often vary in width, so for a mixed pile, measure each board's width and use the average.
The formula
board feet = thickness (in) × width (in) × length (ft) ÷ 12
If you measured the length in inches, divide by 144 instead of 12.
Worked example: ten 2 × 6 boards, 8 ft long
- One board: 2 × 6 × 8 ÷ 12 = 8 board feet.
- Ten boards: 8 × 10 = 80 board feet.
- At $4.50 per board foot that would be $360. Prices vary widely by species and grade, so enter your own.
Hardwood thickness in quarters
| Quarter size | Rough thickness | Typical surfaced (S2S) |
|---|---|---|
| 4/4 | 1 in | about ¾-13/16 in |
| 5/4 | 1¼ in | about 1-1 1/16 in |
| 6/4 | 1½ in | about 1¼-1 5/16 in |
| 8/4 | 2 in | about 1¾ in |
| 12/4 | 3 in | about 2¾ in |
Board feet are figured on the rough thickness, even when you buy the board already planed. That's standard practice, not a markup.
Board feet vs linear feet vs square feet
- Board feet measure volume. Used for hardwood, and sometimes for framing lumber in bulk.
- Linear feet measure length only. Used for trim, molding and most boards at home centers, where the size is fixed.
- Square feet measure surface area. Used for plywood, decking coverage and flooring.
Buying tips
- Buy 15 to 25% extra for furniture work. Knots, checks and grain you don't like all end up as offcuts.
- Check the grade. FAS (first and seconds) gives long clear cuts; #1 Common is cheaper and fine for shorter parts.
- Let it acclimate. Store hardwood in the shop for a week or two before milling so it can reach the room's moisture level.
Questions people ask
How do you calculate board feet?
Multiply thickness in inches × width in inches × length in feet, then divide by 12. A 2 × 6 that is 8 ft long is 2 × 6 × 8 ÷ 12 = 8 board feet.
What is a board foot?
A volume of wood equal to a board 1 inch thick, 12 inches wide and 12 inches long: 144 cubic inches, or 1/12 of a cubic foot.
What does 4/4 and 8/4 mean in lumber?
Hardwood thickness is sold in quarter inches: 4/4 (four quarter) is 1 inch rough, 5/4 is 1¼ inch, 6/4 is 1½, 8/4 is 2 inches and 12/4 is 3 inches. Board feet are calculated on that rough thickness, even though the board is thinner after planing.
Do you use nominal or actual size for board feet?
Nominal, by convention. A 2×4 that actually measures 1½ × 3½ inches is still figured as 2 × 4 when lumber is priced by the board foot. Hardwood is figured on its rough thickness and the actual width.
How many board feet are in a 2x4x8?
5.33 board feet: 2 × 4 × 8 ÷ 12.
Sources and assumptions
- USDA Forest Products Laboratory, Wood Handbook (FPL-GTR-282): a board foot is 144 in³, 1 in × 12 in × 12 in
- National Hardwood Lumber Association rules: hardwood thickness in quarters (4/4 = 1 in)
Last reviewed 27 October 2026. Every formula on this page is checked against the worked example above in our automated tests. Found a problem? Tell us.