Board Foot Calculator
Thickness × width × length ÷ 12 — the hardwood dealer's unit, computed instantly with quarters presets and a cost total at your local price.
Verified against independent hand calculation · sources cited below
4.00 board feet
Dealers bill on rough (nominal) thickness: a surfaced 13/16″ board still sells as 4/4. Measure width and length as the actual board — most yards round length down to the foot.
The formula, shown
BF = T(in) × W(in) × L(ft) ÷ 12 — or with everything in inches, divide by 144. Worked example: three 8/4 boards, 7-1/4″ wide, 10 ft long: 2 × 7.25 × 10 ÷ 12 = 12.08 BF each, 36.25 BF total. At $8.50/BF that’s about $308.
Buying hardwood without surprises
- Quarters name rough thickness. 4/4 = 1″, 5/4 = 1-1/4″, 6/4 = 1-1/2″, 8/4 = 2″ — measured before surfacing.
- Surfaced stock still bills rough. S2S 13/16″ boards sell as 4/4; that’s not a scam, it’s the rule.
- Yards round length down to the foot, and many round width to the nearest 1/2″ — measure the same way they do.
- Budget waste. A cut list total is a floor, not a shopping list: add 20–40%.
Nominal vs. actual: the softwood aisle speaks a different dialect
Hardwood quarters and home-center dimensional lumber both use names that are bigger than the board, but they shrink differently. A 4/4 hardwood board loses thickness to surfacing (1″ rough → about 13/16″ planed) and you still buy the rough inch. A construction “2×4” is a fixed trade size: the American Softwood Lumber Standard pins its dressed dimensions at 1-1/2″ × 3-1/2″, and nobody bills you for the phantom 2″ × 4″ — you pay by the linear foot at the actual size.
The dressed sizes worth memorizing:
1×2 → 3/4″ × 1-1/2″1×4 → 3/4″ × 3-1/2″1×6 → 3/4″ × 5-1/2″1×8 → 3/4″ × 7-1/4″2×4 → 1-1/2″ × 3-1/2″2×6 → 1-1/2″ × 5-1/2″2×8 → 1-1/2″ × 7-1/4″2×10 → 1-1/2″ × 9-1/4″2×12 → 1-1/2″ × 11-1/4″4×4 → 3-1/2″ × 3-1/2″6×6 → 5-1/2″ × 5-1/2″
Note the pattern break: 1× and 2× stock loses 1/2″ of width up through 6″ nominal, then 3/4″ from 8″ nominal on up. If a plan calls for board feet of construction lumber, convention is to figure it on the nominal size — a 2×4 counts as 2″ × 4″ in the formula — which is why an 8-foot 2×4 is quoted as 5.33 BF even though the actual wood works out to just 3.5 BF. For hardwood in this calculator, enter rough thickness (the quarters preset) and the real measured width.
Frequently asked questions
What exactly is a board foot?
A board foot is 144 cubic inches of lumber — the volume of a board 1″ thick, 12″ wide, and 12″ long. The formula: thickness (in) × width (in) × length (ft) ÷ 12. An 8-foot 4/4 board that’s 6″ wide is exactly 4 board feet.
Why did my 4/4 board measure only 13/16″ thick?
Because board feet are billed on rough thickness, before surfacing. A 4/4 (four-quarter) board starts life 1″ thick at the sawmill; after kiln drying and planing it typically lands at 13/16″. You pay for the 1″ — that’s the convention everywhere hardwood is sold.
How many board feet do I need for my project?
Sum the board feet of your cut list, then add 20–40% for waste — defects, grain matching, tear-out, and mistakes. Furniture makers commonly buy 30% over; figured or rustic lumber with knots deserves 40%+.
Is a board foot the same as a linear foot?
No. A linear foot is just length, ignoring width and thickness. A linear foot of 4/4 × 6″ stock is 0.5 board feet; a linear foot of 8/4 × 10″ stock is 1.67 board feet. Dimensional-lumber stores price linear; hardwood dealers price board feet.
Sources & further reading
- National Hardwood Lumber Association — Rules for the Measurement & Inspection of Hardwood & Cypress (board-foot standard)
- Board foot = 144 in³, billed on rough (nominal) thickness — standard U.S. hardwood trade practice
- U.S. Department of Commerce Voluntary Product Standard PS 20 — American Softwood Lumber Standard (nominal vs. actual dressed sizes)
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