A 6×6 is sold and labeled as 6×6, but it actually measures 5½" × 5½". The difference comes from milling and drying — the board starts closer to its named size, then shrinks as it's surfaced smooth and dried to standard moisture content.
Structural posts, porch/pergola posts, heavy fence posts
6x6 is often sold rough-sawn or as reclaimed timber alongside dimensional PT stock — actual size and moisture content can vary more than smaller lumber, so measure before you build around it.
| Nominal Size | Actual Size | Actual (decimal) |
|---|