Board Foot Calculator
| Nominal size | Board feet per 8 ft stick | Cost at $6/bf |
|---|---|---|
| 1 x 4 | 2.67 | $16.00 |
| 1 x 6 | 4.00 | $24.00 |
| 1 x 12 | 8.00 | $48.00 |
| 2 x 4 | 5.33 | $32.00 |
| 2 x 8 | 10.67 | $64.00 |
| 2 x 10 | 13.33 | $80.00 |
| Hardwood quarters | Rough thickness | Finished (surfaced both faces) |
|---|---|---|
| 4/4 | 1.00 in | ≈ 3/4 in |
| 5/4 | 1.25 in | ≈ 7/8 in |
| 6/4 | 1.50 in | ≈ 1 1/8 in |
| 8/4 | 2.00 in | ≈ 1 5/8 in |
| 12/4 | 3.00 in | ≈ 2 5/8 in |
A board foot is a volume, not a piece: 1 inch thick, 12 inches wide, 1 foot long - 144 cubic inches of sawed lumber, the unit hardwood lumberyards quote and the reason a wide board costs multiples of a narrow one at the same length. The arithmetic is one line - thickness in inches x width in inches x length in feet, divided by 12 - but the conventions around it (4/4 stock, nominal vs actual, rough vs surfaced) trip up everyone on their first hardwood run.
Bottom line: a 5/4 walnut board, 8 inches wide and 6 feet long, is 1.25 x 8 x 6 / 12 = 5 board feet - at $12 a board foot that is $60 before tax, and with the standard 15% waste allowance for cutting around defects, plan on buying 5.75 board feet, about $69, to actually finish the project.
The honest part: hardwood is sold rough-cut at nominal thickness, so a 4/4 ("four-quarter") board is a true 1 inch before planing - surfacing both faces takes off roughly 3/8 inch total, landing a finished 5/8 to 3/4 inch. Softwood 2x4s work the other way: sold by the piece, sized to nominal, already surfaced - which is why the lumberyard never quotes softwood in board feet and why the two worlds use different math.
How to use
- Enter thickness in inches - or read it off the hardwood rack's quarter convention (4/4 = 1", 5/4 = 1.25", 8/4 = 2").
- Enter width in inches and length in feet for one board or the whole cut list (use quantity for repeats).
- Add your species' price per board foot and read the cost - then add the 15% waste line before you order.
Frequently asked questions
What is a board foot, exactly?
144 cubic inches: a board 1 inch thick, 12 inches wide, and 1 foot long. The formula is thickness (in) x width (in) x length (ft) / 12 - so any 1-inch-thick board that is 12 inches wide costs you one board foot per foot of length, whatever the species. Missouri Extension's timber guide uses the same definition for log scaling: it is the common standard for sawed lumber on both sides of the sawmill gate.
What does 4/4, 5/4, 8/4 thickness mean?
Quarters of an inch of rough thickness: 4/4 is 1 inch, 5/4 is 1.25, 6/4 is 1.5, 8/4 is 2, 12/4 is 3. The convention comes from sawmills counting quarter-inch layers off the log, and it refers to the rough board before surfacing - after jointing and planing both faces, 4/4 stock finishes at about 3/4 inch. When a plan calls for "1-inch oak," it almost always means buy 4/4; a "2-inch tabletop" means 8/4.
Why does a wide board cost so much more per board foot?
It usually doesn't - per board foot. But wide, clear boards carry a premium because they come from the outside of old, large logs, and the price per board foot for 10-inch white oak can be double the 4-inch price. The calculator's linear math is right for the volume; check the yard's price breaks by width class before assuming the same rate across the rack. Lumberyards also charge by the random length they stock, not your cut list.
How much extra should I buy for waste?
Fifteen percent is the standard allowance for straight parts from good stock - crosscut losses, planer snipe, one hidden check. Go 25-30% when the design uses the grain direction of the board (river-table tops, matched cabinet doors) or when buying lower grades with more defects to cut around. Ordering exactly your cut list is the classic first-project mistake: the board you need in 6 feet comes in 8, and the defect always lands where your joint is.