Board Foot Calculator
One line per board size — total footage and cost, tallied the way the yard bills it.
| Qty | Thickness | Width (in) | Length (ft) | $/BF | BF | |
|---|---|---|---|---|---|---|
| 30.00 | ||||||
| 18.50 | ||||||
| 18.33 |
Board feet
66.83 BF
- Pieces
- 12 boards on 3 lines
- Net board feet
- 66.83 BF
- Volume
- 5.57 ft³
- Net cost
- $476.04
- Blended price
- $7.12/BF
Yards apply a minimum footage per board and often round the tally up — treat this as the number to check the ticket against, not the exact ticket.
Need to know what it weighs in the truck? Use the lumber weight calculator →
How this is calculated
BF per board = thickness(in) × width(in) × length(ft) / 12
= thickness(in) × width(in) × length(in) / 144
line BF = BF per board × quantity
buy = total BF × (1 + waste%)A board foot is a volume, not a length: 144 cubic inches, the size of a one inch board a foot square. Dividing by 12 rather than 144 is just the shortcut that comes from entering length in feet. With nominal billing the quarter you pick sets the thickness, so surfaced 4/4 stock that mikes 13/16 still calculates at a full inch — that is the wood the mill sawed and dried, and it is what you are paying for.
Width rounding follows the NHLA tally convention of measuring average width to the nearest inch. It moves the total more than people expect: a stack of boards averaging 7.6 inches tallies at 8, roughly 5% more footage. Leave it off when you are estimating what you can cut out of the pile, since your usable width is the narrowest point rather than the average.
Board feet by common board size
| Board | Per foot of length | 8 ft | 10 ft | 12 ft |
|---|---|---|---|---|
| 4/4 × 4" | 0.33 | 2.67 | 3.33 | 4.00 |
| 4/4 × 6" | 0.50 | 4.00 | 5.00 | 6.00 |
| 4/4 × 8" | 0.67 | 5.33 | 6.67 | 8.00 |
| 4/4 × 10" | 0.83 | 6.67 | 8.33 | 10.00 |
| 4/4 × 12" | 1.00 | 8.00 | 10.00 | 12.00 |
| 5/4 × 6" | 0.63 | 5.00 | 6.25 | 7.50 |
| 6/4 × 8" | 1.00 | 8.00 | 10.00 | 12.00 |
| 8/4 × 6" | 1.00 | 8.00 | 10.00 | 12.00 |
| 8/4 × 8" | 1.33 | 10.67 | 13.33 | 16.00 |
| 12/4 × 8" | 2.00 | 16.00 | 20.00 | 24.00 |
Every figure here comes from the same function the calculator above runs, so the table cannot drift from the tool. Note the pattern in the first column: for 4/4 stock the board feet per running foot is simply the width divided by 12, which is why a 4/4 × 12 board is the easy one — one board foot per foot of length.
Quarter thickness in plain inches
| Quarter | Rough | Typical surfaced (S2S) | Common use |
|---|---|---|---|
| 4/4 | 1" | 13/16" | Panels, drawer fronts, most casework |
| 5/4 | 1 1/4" | 1 1/16" | Stair treads, thick tops, exterior trim |
| 6/4 | 1 1/2" | 1 5/16" | Table aprons, chair parts |
| 8/4 | 2" | 1 3/4" | Legs, thick frames, workbench parts |
| 10/4 | 2 1/2" | 2 1/4" | Heavy legs, turnings |
| 12/4 | 3" | 2 3/4" | Bench tops, large turnings |
| 16/4 | 4" | 3 3/4" | Posts, bowl blanks |
Surfaced dimensions vary by mill; the ones above are the common results of surfacing two faces. If you buy rough and plane it yourself you keep more thickness, which is the real reason to buy rough on anything where a sixteenth of an inch matters.
Frequently asked questions
How do you calculate board feet?
Multiply thickness in inches by width in inches by length in feet, then divide by 12. A board foot is 144 cubic inches, the volume of a piece 1 inch thick, 12 inches wide and 12 inches long. If you have the length in inches instead, multiply all three dimensions and divide by 144 — same answer, different arithmetic.
Is a board foot the same as a linear foot?
No, and confusing them is the most expensive mistake at the lumber counter. A linear foot measures length only, so a 1x4 and a 1x12 are both one linear foot per foot of length. Board feet measure volume, so that same foot of 1x12 is three times the board footage of the 1x4. Softwood at a home center is often priced per linear foot or per piece, while hardwood is nearly always priced per board foot.
Do I use the rough or the planed thickness?
The rough thickness, which is what the quarter system names. A 4/4 board that has been surfaced to 13/16 of an inch still bills as a full inch, because you are paying for the wood the mill sawed and dried, not what survived the planer. That is why the toggle above defaults to nominal — switch it only if you are measuring finished stock for a weight or volume estimate rather than pricing a purchase.
How is width measured on a rough board?
Under NHLA hardwood rules a board is tallied at its average width, rounded to the nearest inch, measured clear of the wane. A board that mikes 7.6 inches tallies as 8. Turn on width rounding if you want to match how the yard will write the ticket; leave it off if you are estimating what you can actually cut out of the board, which is always less.
How much extra should I buy?
For furniture from rough lumber, 25 to 40% over your net cut list is normal, and the low end of that assumes clear stock and forgiving grain. You lose material to jointing, planing, ripping out defects, snipe and the cutoffs that are just slightly too short. Projects with grain matching or curved parts push past 50%, and the cost of a second trip usually exceeds the cost of the extra board.
Why does the yard total differ from mine?
Three usual causes: they tallied widths to the nearest inch and you measured to the tenth, they billed 4/4 on stock you measured at 13/16, or they applied a minimum footage per board. Bring both numbers and it resolves in a minute. Lumber is one of the few purchases where the seller measurement rules are published — NHLA sells the grading handbook — so the disagreement is always checkable.
Results are planning estimates. Yards differ on minimum footage per board, on how wane and defects are deducted, and on whether surfacing is billed separately. Confirm the tally rules before a large order, and expect the invoice to round in the seller favour.