The board foot formula
A board foot is <strong>144 cubic inches — one inch thick, 12 inches wide, 12 inches long</strong>. 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 <strong>actual milled thickness</strong>: 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.