Board feet in a 6×6×12

There are two honest answers. The wood you actually carry out of the store is 30.25 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 36.00 BF, because board feet are by convention figured on the nominal 6″ × 6″ name.

The math, both ways

Which one do you want? If you're figuring weight, volume, or "how much wood is that really," use 30.25. If you're comparing against hardwood priced per board foot, or reading a mill tally, use 36.00 — 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.

Twelve feet divides evenly into 16″ and 24″ on-center layouts, which makes it the blocking-and-plate length framers reach for. It still fits in most garages and on most roof racks — the last length that's easy to haul without flags and straps.

Heft check: at its true 5.5″ × 5.5″ section, a 12′ board holds 2.52 ft³ of wood — about 88 lb kiln-dried, and closer to 139 lb dripping fresh off the pressure-treated rack — a genuine two-person lift.

What that volume costs at hardwood prices

Open this size in the planner

Related: 6×6×8 · 6×6×10 · all sizes