The formula
BF = (thickness in × width in × length in) / 144
For length in feet instead of inches, use BF = (T × W × Lft) / 12. Always measure thickness in quarters (4/4, 5/4, 8/4) because lumberyards bill from rough thickness, not finished thickness.
Example: 100 bd ft of 8/4 walnut
Walnut rough-cut at 8/4 (nominally 2"), 10" wide, and 8 feet long: (2 × 10 × 96) / 144 = 13.33 bd ft per board. At $12 per board foot, that’s $160 per board. Eight boards puts you right at 100 bd ft and about $1,280 before tax.
Why it matters
Small counting errors compound fast. If you’re off by a single board in your plan, you’ll either run short mid-project or overbuy by 12% on a species that costs $15–25 per foot. Dead On keeps a running total and optionally a cost column so you can stop mentally juggling on the way to the yard.
Step-by-step
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1
Measure thickness
Use rough thickness in inches (4/4 = 1", 5/4 = 1.25", 8/4 = 2", etc.).
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2
Measure width
Use the board’s actual width at its widest usable point, in inches.
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3
Measure length
Total usable length in inches (or use the feet formula).
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4
Multiply and divide by 144
Result is the board foot count for that one piece.
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5
Add boards together
Sum the individual board feet for a load total. Dead On does this automatically.
Skip the math. Build the diagram.
Dead On does the board foot calculator and 12 other woodworking calculators with visual diagrams, offline, on every Apple device signed into your Apple ID.
Download Dead On — FreeFrequently asked questions
What is a board foot?
A board foot is a unit of lumber volume equal to 144 cubic inches — a 1" × 12" × 12" piece. Lumberyards price hardwood by the board foot.
Do I use rough or finished thickness?
Always use the rough thickness that the mill bills you for: 4/4 = 1", 5/4 = 1.25", 8/4 = 2". You pay for rough; you get finished after milling and planing.
How do I account for waste?
Add 15–25% on top of your final part-list board foot total for milling, snipe, and defect loss. Figured woods and narrow boards need more.
Can Dead On track multiple boards with prices?
Yes. The Pro version adds a running total with cost per board foot so you can see the lumber bill build up as you add pieces.