Board feet in a 2×12×8
There are two honest answers. The wood you actually carry out of the store is 11.25 board feet — a 2×12 really measures 1.5″ × 11.25″. But if you're pricing or trading lumber, the industry counts this board as 16.00 BF, because board feet are by convention figured on the nominal 2″ × 12″ name.
The math, both ways
trade (nominal): 2″ × 12″ × 96″ ÷ 144 = 16.00 BF
Which one do you want? If you're figuring weight, volume, or "how much wood is that really," use 11.25. If you're comparing against hardwood priced per board foot, or reading a mill tally, use 16.00 — the whole trade runs on nominal, for the historical reasons on our nominal vs actual page. (Construction lumber itself is usually priced per piece, so at the store neither number appears on the shelf tag.)
What a 2×12 is for
The 2×12 is the biggest common dimensional board, and it has one famous job: stair stringers. Cutting the sawtooth for treads and risers eats so much width that only a 2×12 leaves enough uncut wood (the code minimum "throat") to carry the load. It's also the long-span joist, the ridge board, and the site-built beam.
Big boards concentrate the drying stresses of the tree, so a stack of 2×12s hides more crook and wane than a stack of 2×4s. Sight down every one, and plan cuts around the heart center if a board contains it.
Eight feet is the default length — it matches the ceiling, fits inside a pickup bed with the tailgate down, and wastes the least when cut for typical walls. It's usually the cheapest per foot, too, because it's the volume seller.
Heft check: at its true 1.5″ × 11.25″ section, a 8′ board holds 0.94 ft³ of wood — about 33 lb kiln-dried, and closer to 52 lb dripping fresh off the pressure-treated rack.
What that volume costs at hardwood prices
| Price per BF | Actual wood (11.25 BF) | Trade tally (16.00 BF) |
|---|---|---|
| $3.00 | $33.75 | $48.00 |
| $5.00 | $56.25 | $80.00 |
| $7.00 | $78.75 | $112.00 |
| $10.00 | $112.50 | $160.00 |