Board feet in a 6×6×8
There are two honest answers. The wood you actually carry out of the store is 20.17 board feet — a 6×6 really measures 5.5″ × 5.5″. But if you're pricing or trading lumber, the industry counts this board as 24.00 BF, because board feet are by convention figured on the nominal 6″ × 6″ name.
The math, both ways
trade (nominal): 6″ × 6″ × 96″ ÷ 144 = 24.00 BF
Which one do you want? If you're figuring weight, volume, or "how much wood is that really," use 20.17. If you're comparing against hardwood priced per board foot, or reading a mill tally, use 24.00 — 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 6×6 is for
The 6×6 is what deck codes increasingly demand where a 4×4 once sufficed — and not just for strength: a 6×6 post is wide enough to notch, letting the beam sit on a shoulder of solid wood instead of hanging on bolts alone, which is the detail inspectors love. It's also the retaining-wall timber, the mailbox post that survives the snowplow, and the pergola column.
Every 6×6 contains the tree's center, so deep surface checks are a certainty, not a defect — they rarely matter structurally. What does matter is the treatment tag: posts touching soil need "ground contact" rated stock. And plan the lift; this is the size where lumber stops being a one-person material.
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 5.5″ × 5.5″ section, a 8′ board holds 1.68 ft³ of wood — about 59 lb kiln-dried, and closer to 92 lb dripping fresh off the pressure-treated rack — a genuine two-person lift.
What that volume costs at hardwood prices
| Price per BF | Actual wood (20.17 BF) | Trade tally (24.00 BF) |
|---|---|---|
| $3.00 | $60.50 | $72.00 |
| $5.00 | $100.83 | $120.00 |
| $7.00 | $141.17 | $168.00 |
| $10.00 | $201.67 | $240.00 |