The board foot formula
A board foot is 144 cubic inches — one inch thick, 12 inches wide, 12 inches long. Hardwood is rough-sawn and priced by actual thickness, so the formula is thickness × width × length ÷ 144, multiplied by quantity. A 2×6 that's 8 feet long is 8 board feet before milling.
Rough size, not nominal size
Unlike construction lumber's nominal sizing, hardwood board footage uses the actual milled thickness: a '4/4' board is 1 inch rough, planed to 3/4. Measure the real thickness with calipers, count the longest straight length even past knots, and hardwood yards will round up per board.
Sources and standards
Where these figures come from
Every formula on this page is implemented from the published reference material below. Where a value depends on a regional code, the calculator lets you override it rather than assuming one jurisdiction.
- American Wood Council — span tables, lumber design values and the Wood Frame Construction Manual.
- APA — The Engineered Wood Association — panel span ratings and sheathing installation guidance.
Figures, formulas and reference tables last verified: 19 September 2026.