Board feet explained: how lumber is measured and priced
If you've looked at a woodworker's quote or a hardwood dealer's price list, you've seen lumber priced "per board foot". Here's what that means, and why it matters when you commission a piece.
What a board foot is
A board foot is a unit of volume: a piece of wood 1 inch thick, 12 inches wide and 12 inches long. That's 144 cubic inches. The formula is:
board feet = thickness (in) × width (in) × length (ft) ÷ 12
A board 1 inch thick, 6 inches wide and 8 feet long is 1 × 6 × 8 ÷ 12 = 4 board feet. A board 2 inches thick, 8 inches wide and 10 feet long is 2 × 8 × 10 ÷ 12 = 13.3 board feet.
Our board foot calculator does the arithmetic for a whole stack, adds a waste allowance and multiplies by a price per board foot if you have one. It also works in millimeters and meters.
Quarters: 4/4, 6/4, 8/4
Hardwood dealers describe rough-sawn thickness in quarters of an inch. 4/4 ("four quarter") is 1 inch, 6/4 is 1½ inches, 8/4 is 2 inches. That's the thickness when the board was sawn and dried, before planing. A 4/4 board usually ends up around ¾ inch thick once both faces are flattened, but you pay for the rough thickness.
Softwood dimensional lumber, like a 2×4, is different: it's named by nominal size and sold planed (an actual 2×4 measures about 1½ × 3½ inches), and it's usually priced per piece rather than per board foot.
Why the maker buys more than your piece contains
A finished tabletop might contain 20 board feet of wood, but the maker will buy noticeably more. Boards are rarely perfectly flat or straight, so flattening them removes thickness. Ends are often checked (split) and get cut off. Knots, sapwood and other defects are cut around. Parts rarely divide neatly into board lengths, so there are offcuts. And for a good-looking top, the maker picks boards that match in color and grain, which means rejecting some.
That's why quotes include a waste allowance. How much depends on the lumber and the design: clear, straight stock and a simple cut list waste less; figured wood and long matched panels waste more.
How species changes the cost
The price per board foot differs between species, and between grades and widths of the same species. As a rule, pine and poplar are the least expensive, oak and maple are in the middle, and cherry and walnut cost more. Prices change by region and over time, so the best source is a local hardwood dealer's current list.
For most furniture, though, lumber is the smaller part of the bill. A dining table might take a few dozen board feet of wood and many dozens of hours of shop time. HomeAdvisor's cost guide puts custom woodworking labor at $50 to $100 an hour plus materials. That's why switching species changes a quote less than you might expect, while simplifying the design can change it a lot.
When you write your brief
You don't need to calculate board feet to commission a piece; the maker will. But giving accurate finished dimensions, the species you want and a budget lets them work out the lumber quickly and bid accurately.
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