A board foot is a volume — 144 cubic inches — not an area, which is why it trips people up. And hardwood is charged at the size it was sawn, not the size it is after planing, so the board in your hand is smaller than the board on the invoice.
Enter each size of board and how many. Add rows for different sizes and it totals them.
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144 cubic inches of it — thickness × width × length in inches, divided by 144. That is why it trips people up: it is not an area, and it cannot be converted to square feet without knowing the thickness. A piece 2 in thick, 6 in wide and 8 ft long is 8 board feet. If someone quotes a price per square foot for hardwood, ask what thickness they mean.
Not the size it is after planing. The usual convention for rough hardwood is nominal for thickness and actual for width and length: thickness is quoted at the sawn size in quarters — 4/4 is one inch, 8/4 is two — while width and length are what you can actually measure. So the board in your hands is thinner than the board on the invoice, and that is normal rather than sharp practice.
Add 20–30% for rough sawn material and less for surfaced: random widths mean offcuts, edges need straightening, and knots and splits have to be cut around. Acclimatise hardwood before you cut it — in the space it will live in, stickered so air moves round it, for at least a week and preferably longer. And for comparing quotes across markets: 424 board feet to the cubic metre. The units are not just different, the conventions behind them are too.
144 cubic inches of timber — thickness times width times length in inches, divided by 144. It is a volume, not an area, which is the source of most of the confusion around it.
You cannot, without knowing the thickness. Board feet measure volume and square feet measure area. If a supplier quotes hardwood per square foot, ask what thickness that price assumes.
Because rough hardwood is charged at the sawn size, not the planed size. Thickness is quoted nominally in quarters — 4/4 is one inch, 8/4 is two — while width and length are actual. Planing removes material after measurement.
424. Worth remembering when comparing an American quote with a European one, because the units and the measuring conventions both differ.