Nominal vs. Actual Lumber Sizing
In North American construction, dimensional lumber sizes refer to rough-sawn green timber before planing. Surfaced four sides (S4S) kiln-dried lumber reduces the thickness and width significantly.
| Nominal Size | Actual (Inches) | Actual (Metric mm) | Area (sq. in.) |
|---|---|---|---|
| 2×4 | 1-1/2″ × 3-1/2″ | 38 × 89 mm | 5.25 in² |
| 2×6 | 1-1/2″ × 5-1/2″ | 38 × 140 mm | 8.25 in² |
| 2×8 | 1-1/2″ × 7-1/4″ | 38 × 184 mm | 10.88 in² |
| 2×10 | 1-1/2″ × 9-1/4″ | 38 × 235 mm | 13.88 in² |
| 2×12 | 1-1/2″ × 11-1/4″ | 38 × 286 mm | 16.88 in² |
| 4×4 | 3-1/2″ × 3-1/2″ | 89 × 89 mm | 12.25 in² |
| 6×6 | 5-1/2″ × 5-1/2″ | 140 × 140 mm | 30.25 in² |