How Many Board Feet In a 6x6x8
20.167 board feet
- Actual size: 5.5" x 5.5" (nominal 6x6")
- Length: 8 ft
Methodboard feet = (thickness x width x length in feet) / 12, using the ACTUAL dressed dimension.
Using the nominal 6x6" number instead of the actual dimension would overstate this by a meaningful margin — see /reference/nominal-vs-actual-2x4/.
An 8-foot 6x6 timber contains 20.167 board feet (exactly 121/6) — the single largest board-foot figure among every dimension-and-length combination this site's answer pages cover, driven by a genuinely large 5.5" x 5.5" actual cross-section rather than an unusual length.
Why this one specifically
6x6 is timber-framing and heavy-post stock, well outside ordinary dimensional-lumber territory, and it's priced and sourced differently from a standard 2x or 4x board as a result — a real 6x6 timber is often special-order or comes from a dedicated timber supplier rather than a standard lumberyard rack, and board-foot pricing at that scale involves real money per piece.
What moves the number
This uses the actual 5.5" x 5.5" dressed dimension; some 6x6 timber, particularly rough-sawn structural stock, is sold closer to a true nominal 6" x 6" rather than surfaced down the way dimensional 2x lumber is — confirm which convention applies before pricing a real order, since the difference between the two at this scale is substantial.
Compare against the 4x4x8 for the smaller common post size, or the 2x12x12 for the largest dimensional (non-timber) size this site tracks, and run other lengths through the board foot calculator.