Free lumber tool
Board foot calculator
Figure lumber the way the yard does. Enter thickness, width, length, and how many boards, and get board feet per board, the total, and the cost at your price per board foot.
Calculator
Total board feet
4 BF
- Per board
- 4 BF
Buying for a project? Order 15 to 30% extra to cover defects, grain matching, and trim cuts.
The board foot formula
One board foot is 144 cubic inches of lumber: a piece 1″ thick, 12″ wide, and 12″ long.
Length in inches
(T × W × L) ÷ 144
A 1" × 6" × 96" board is (1 × 6 × 96) ÷ 144 = 4 board feet.
Length in feet
(T × W × L) ÷ 12
Same board: (1 × 6 × 8) ÷ 12 = 4 board feet. One less step.
Total cost
Board feet × price per BF
4 board feet of $4.50/BF hardwood costs $18. Price varies by species and grade.
Quarter sizes, explained
Hardwood thickness is quoted in quarters of an inch, measured rough sawn before surfacing. You buy board feet on the rough thickness, and the planer takes its share on the way to a finished board.
That’s why 4/4 stock ends up around 13/16″ after surfacing two faces, and why a project that needs a true inch calls for 5/4 lumber.
| Quarter size | Rough thickness | Typical surfaced (S2S) |
|---|---|---|
| 4/4 | 1" | 13/16" |
| 5/4 | 1-1/4" | 1-1/16" |
| 6/4 | 1-1/2" | 1-5/16" |
| 8/4 | 2" | 1-3/4" |
| 10/4 | 2-1/2" | 2-1/4" |
| 12/4 | 3" | 2-3/4" |
Why lumber is sold by volume
A softwood 2x4 comes in standard sizes, so it’s sold by the piece. Hardwood doesn’t work that way: sawmills cut each log for the best yield, so boards arrive in random widths and lengths. The board foot puts every odd-sized board on the same scale, 144 cubic inches at a time.
That’s also why estimating matters. A cutting list tells you the net material in a project; the board foot tally tells you what to buy. The gap between those two numbers, waste, defects, and grain matching, is where experienced buyers add 15 to 30%.
Board foot FAQs
What is a board foot?
A board foot is the standard volume measure for hardwood lumber: one board foot equals a piece 1 inch thick, 12 inches wide, and 12 inches long, or 144 cubic inches in any shape. Hardwood is sold by the board foot because boards come in random widths and lengths, unlike dimensional softwood that is sold by the piece.
How do I calculate board feet?
Multiply thickness in inches by width in inches by length in inches, then divide by 144. If your length is in feet, divide by 12 instead. Multiply by the number of boards for a total. Example: ten 4/4 boards, 6 inches wide and 8 feet long, are (1 x 6 x 8) / 12 = 4 board feet each, 40 board feet total.
What does 4/4, 5/4, or 8/4 lumber mean?
Hardwood thickness is quoted in quarters of an inch, measured rough sawn: 4/4 ("four quarter") is 1 inch, 5/4 is 1-1/4 inches, 8/4 is 2 inches. Surfacing removes material, so 4/4 stock typically finishes around 13/16 inch. You pay board feet on the rough thickness, not the surfaced result.
How many board feet are in a 2x4x8?
Using nominal dimensions, a 2x4 that is 8 feet long is (2 x 4 x 8) / 12 = 5.33 board feet. Note that board feet always use nominal sizes: an actual 2x4 measures 1.5 by 3.5 inches, but it still tallies as 2 by 4.
Why does lumber under 1 inch still count as 4/4?
By lumber tally convention, stock thinner than 1 inch is counted as a full inch when figuring board feet, because it was milled from 4/4 rough stock. This calculator applies that rule automatically and tells you when it does.
How much extra lumber should I order?
Plan on 15 to 30% over your net requirement. Knots, checks, warp, grain matching, and trim cuts all eat material. Rough, lower-grade lumber needs more allowance; surfaced, select-grade stock needs less. Running out mid-job costs more than the overage.
How much does hardwood cost per board foot?
It varies widely by species, grade, thickness, and region: domestic species like oak, maple, and cherry commonly run a few dollars per board foot, while figured or exotic stock can run several times that. Thicker stock (8/4 and up) usually costs more per board foot than 4/4. Get current prices from your local supplier.
Processing lumber every day?
When board feet turn into truckloads, the machinery matters. We help shops choose woodworking machinery that gets more finished parts out of every board, from moulders and rip saws to CNC routers. Curious what an upgrade returns? Run the machine ROI calculator.