Turn a pile of boards into board feet, or a board-foot order into running feet of a given width and thickness. Hardwood is priced by the board foot, so this is the number to get right before you go to the yard.
A board foot is a piece of wood 1 in thick, 12 in wide and 1 ft long — 144 cubic inches. A linear foot is just a foot of length, whatever the cross-section. The two only agree for a 1 × 12; for everything else you need the conversion.
Hardwood dealers sell rough lumber by the board foot, using the nominal thickness in quarters (4/4 = 1 in, 8/4 = 2 in) and the actual width of each board. Softwood framing and trim are usually sold by the piece or the linear foot. Mixing up the two is the most common way to buy too little wood.
Multiply thickness and width in inches by length in feet and the number of pieces, then divide by 12. To go the other way, divide board feet by the board feet per linear foot of your section.
BF = T × W × L(ft) × N ÷ 12 · LF = BF × 12 ÷ (T × W)
| Thickness | Width | BF per linear ft | 8 ft board | Linear ft per BF |
|---|---|---|---|---|
| 4/4 (1 in) | 4 in | 0.33 | 2.67 | 3.00 |
| 4/4 (1 in) | 6 in | 0.50 | 4.00 | 2.00 |
| 4/4 (1 in) | 8 in | 0.67 | 5.33 | 1.50 |
| 4/4 (1 in) | 10 in | 0.83 | 6.67 | 1.20 |
| 4/4 (1 in) | 12 in | 1.00 | 8.00 | 1.00 |
| 5/4 (1.25 in) | 6 in | 0.62 | 5.00 | 1.60 |
| 6/4 (1.5 in) | 6 in | 0.75 | 6.00 | 1.33 |
| 8/4 (2 in) | 6 in | 1.00 | 8.00 | 1.00 |
| 8/4 (2 in) | 8 in | 1.33 | 10.67 | 0.75 |
| 8/4 (2 in) | 10 in | 1.67 | 13.33 | 0.60 |
Nominal sizes, the way most hardwood tallies are written. The “8 ft board” column is the calculator run on one piece 8 ft long.
How many feet of 7 in cherry is 30 board feet? Enter 4/4, 7 in wide, and 30 in the reverse box. The answer is 51.43 linear feet, about six and a half 8 ft boards. If your cut list needs 30 BF of finished parts, buy more — see the waste note below.
One wide 8/4 plank. 2 in × 9 in × 10 ft: 2 × 9 × 10 ÷ 12 = 15 board feet. At a hypothetical $9 per board foot, that plank is $135 before tax, which is why measuring width carefully at the yard matters.
Framing lumber, nominal versus actual. Twelve 2×4s, 8 ft long. Nominal: 2 × 4 × 8 × 12 ÷ 12 = 64 BF. Choose custom thickness 2 and tick “dressed” to use the actual 1½ × 3½ in section and the volume drops to 42 BF. Yards that quote framing in board feet normally mean the nominal figure.
Rough hardwood has checks at the ends, knots, sapwood you may not want, and boards that are not quite flat. After milling and cutting around defects, furniture makers commonly see 20–40% of the board footage end up as offcuts, more with lower grades or strict colour matching. A practical approach: total the board feet of your finished parts, then multiply by 1.3 to 1.5 depending on grade and how picky the project is.
Thickness loss matters too. 4/4 rough lumber usually surfaces to about ¾–13/16 in; if your design needs a full 1 in, buy 5/4.
Add each board as you pull it from the rack. Here is a small mixed load worked through the calculator one board at a time:
| Board | Size (T × W × L) | Board feet |
|---|---|---|
| 4/4 cherry | 1 in × 7 in × 8 ft | 4.67 |
| 4/4 cherry | 1 in × 9 in × 10 ft | 7.50 |
| 5/4 maple | 1.25 in × 5 in × 12 ft | 6.25 |
| 8/4 walnut | 2 in × 6 in × 8 ft | 8.00 |
| Total | 26.42 |
Price each species separately — walnut and maple are rarely the same price per board foot — and add your waste allowance before deciding whether you have enough.
Surfaced hardwood (S2S or S4S) is usually still invoiced on its rough nominal thickness, so a ¾ in surfaced board is billed as 4/4. That makes surfaced stock look more expensive per board foot than it is; you are paying for the milling and the waste the yard has already removed.
Thickness in quarters of an inch: 4/4 is 1 in, 5/4 is 1¼ in, 6/4 is 1½ in, 8/4 is 2 in. It refers to rough thickness before surfacing.
Each board’s width is measured, often rounded to the nearest inch, and multiplied by length and thickness. Some yards have their own rounding rules, so their tally can differ slightly from yours.
No, sheet goods are sold by the sheet. Board feet apply to solid lumber.
Yes. Change the length unit to inches and the calculator converts it to feet for you.