What is a board foot?
A board foot is the standard unit for buying and pricing hardwood lumber in the US and Canada. One board foot is the volume of a piece one inch thick, twelve inches wide, and twelve inches long — 144 cubic inches of wood.
Because rough hardwood is sold by the board foot rather than by the piece, knowing the board footage of a board tells you what it should cost. It's abbreviated bd ft, BF, or FBM.
How to calculate board feet
Multiply the three dimensions in inches and divide by 144:
If the length is in feet, use (T × W × L) ÷ 12 instead. For more than one identical board, multiply the result by the quantity. The calculator above handles all of this — including feet-to-inches — automatically.
Quarter (4/4) thickness
Hardwood is usually called out in quarter-inches of rough thickness. Tap a chip above or type the fraction — the math is the same either way:
- 4/4 = 1 inch
- 5/4 = 1¼ inch
- 6/4 = 1½ inch
- 8/4 = 2 inch
- 12/4 = 3 inch
Always calculate on the rough dimensions you're billed for — not the smaller finished size after planing.
Worked example
A single 8/4 board, 6 inches wide and 8 feet long:
2 × 6 × 96 ÷ 144 = 8 board feet. At $6/bf, that's $48.
Common questions
Is a board foot the same as a linear foot?
No. A linear foot measures length only. A board foot measures volume — it accounts for thickness and width too, which is why two boards of the same length can have very different board footage.
Do I use rough or finished dimensions?
Use the rough (nominal) dimensions the lumber is sold and priced at. A board planed down to ¾ inch is still billed as 4/4 (1 inch) stock.
How do I price a whole project?
Enter each board and press "Add to tally." The running total sums board feet and cost across your entire cut list, so you can price a full build at once.
How much waste should I add?
A common rule of thumb: add about 10–15% for clean, straight cuts in select lumber, 15–20% for a typical project, and 25–30% for rough-sawn stock or intricate work with lots of offcuts. Tap “+ Add waste calc” in the cut-list tally to add your percentage — it buffers your total board feet and cost so you order enough the first time.
Does this work in metric?
Yes. Switch to "Metric" to enter centimetres and metres — the result is still shown in board feet, since that's how lumber is priced.