How Many Board Feet In a 4x4x8
8.167 board feet
- Actual size: 3.5" x 3.5" (nominal 4x4")
- Length: 8 ft
Methodboard feet = (thickness x width x length in feet) / 12, using the ACTUAL dressed dimension.
Using the nominal 4x4" number instead of the actual dimension would overstate this by a meaningful margin — see /reference/nominal-vs-actual-2x4/.
An 8-foot 4x4 post contains 8.167 board feet (exactly 49/6) — nearly identical to a 2x12x8's board-foot count despite looking like a much smaller piece, because a square 3.5" x 3.5" cross-section packs more volume than its footprint suggests at a glance.
Why this one specifically
4x4 posts are bought for fence and deck applications where the piece stands vertical rather than lying flat as a joist or stud does — the board-foot figure here matters less for structural span calculations (posts aren't usually spec'd that way) and more for pricing, since board feet is still the unit rough and specialty post stock gets sold by.
What moves the number
This uses the actual 3.5" x 3.5" dressed dimension; posts sold at true nominal 4" x 4" rough dimensions (less common, but they exist for certain post applications) would contain meaningfully more board feet than this dressed-size figure — always confirm which convention a specific supplier is using before ordering by board foot.
Compare against the 6x6x8 for the next post size up, or the matching weight at how much a 4x4 post weighs, and run other lengths through the board foot calculator.