How to Calculate Board Feet (and Log Scaling Rules)
The board foot is how lumber is bought and sold. The formula takes a minute; the scaling rules and pricing traps take a bit more.
What a board foot is
A board foot (BF) is a volume unit: a piece 12 inches wide, 12 inches long and 1 inch thick — 144 cubic inches. It does not matter what the shape is; any stack of wood can be converted to board feet. Lumber in North America is priced per board foot, so every estimate starts here.
The formula
BF = thickness (in) × width (in) × length (ft) ÷ 12 — or, with the length in inches, ÷ 144. A 2×6 board 8 feet long is 2 × 6 × 8 ÷ 12 = 8 BF using nominal dimensions. Hardwood is usually sold by actual (true) measured width and thickness, while dimension softwood trades on nominal sizes — know which convention your supplier uses.
Log scaling: Doyle, Scribner, International
Whole logs are measured with log rules that estimate recoverable lumber. Doyle ((d−4)² × L ÷ 16) heavily undervalues small logs — sellers love it, buyers don't. International 1/4-inch is the most generous and most consistent; Scribner sits in between. The same log can 'shrink' 30% just by switching rules, so agree on the rule before the truck loads.
Rough vs surfaced: where volume disappears
Rough-sawn lumber is measured before planing and drying. Surfaced (S4S) stock has lost thickness and width — a '1-inch' board is 3/4 inch after surfacing. If you buy rough and dress it yourself, budget the planing loss; if you buy dressed, pay for the board feet you actually receive, not the nominal count.
Let the calculator do the scaling
The Board feet calculator converts any mix of boards to board feet, applies the common log rules, and prices the result — including the waste percentage for your own cutting list.