American standard lumber (North American) is sold by nominal dimensions which are larger than the actual finished size. The difference is due to planing (dressing) and drying shrinkage.
| Nominal (in) | Actual (in) | Actual (mm) | Dressed | Common Use |
|---|---|---|---|---|
| 1x2 | 3/4" × 1-1/2" | 19 × 38 | S4S | Trim, furring |
| 1x3 | 3/4" × 2-1/2" | 19 × 64 | S4S | Trim, shelving |
| 1x4 | 3/4" × 3-1/2" | 19 × 89 | S4S | Trim, siding |
| 1x6 | 3/4" × 5-1/2" | 19 × 140 | S4S | Trim, decking |
| 1x8 | 3/4" × 7-1/4" | 19 × 184 | S4S | Trim, shelving |
| 1x10 | 3/4" × 9-1/4" | 19 × 235 | S4S | Trim, flooring |
| 1x12 | 3/4" × 11-1/4" | 19 × 286 | S4S | Trim, shelving |
| 2x2 | 1-1/2" × 1-1/2" | 38 × 38 | S4S | Framing, blocking |
| 2x3 | 1-1/2" × 2-1/2" | 38 × 64 | S4S | Framing, furring |
| 2x4 | 1-1/2" × 3-1/2" | 38 × 89 | S4S | Wall framing, studs |
| 2x6 | 1-1/2" × 5-1/2" | 38 × 140 | S4S | Floor joists, rafters |
| 2x8 | 1-1/2" × 7-1/4" | 38 × 184 | S4S | Floor joists, beams |
| 2x10 | 1-1/2" × 9-1/4" | 38 × 235 | S4S | Floor joists, headers |
| 2x12 | 1-1/2" × 11-1/4" | 38 × 286 | S4S | Floor joists, beams |
| 4x4 | 3-1/2" × 3-1/2" | 89 × 89 | S4S | Posts, columns |
| 4x6 | 3-1/2" × 5-1/2" | 89 × 140 | S4S | Posts, heavy framing |
| 4x8 | 3-1/2" × 7-1/4" | 89 × 184 | S4S | Heavy framing, beams |
| 4x10 | 3-1/2" × 9-1/4" | 89 × 235 | S4S | Heavy framing, beams |
| 4x12 | 3-1/2" × 11-1/4" | 89 × 286 | S4S | Heavy framing, beams |
| 6x6 | 5-1/2" × 5-1/2" | 140 × 140 | S4S | Posts, large columns |
| 6x8 | 5-1/2" × 7-1/2" | 140 × 191 | S4S | Heavy posts, beams |
| 6x10 | 5-1/2" × 9-1/2" | 140 × 241 | S4S | Heavy beams, girders |
| 6x12 | 5-1/2" × 11-1/2" | 140 × 292 | S4S | Heavy beams, girders |
| 8x8 | 7-1/2" × 7-1/2" | 191 × 191 | S4S | Large posts, columns |
| 8x10 | 7-1/2" × 9-1/2" | 191 × 241 | S4S | Large beams, girders |
| 8x12 | 7-1/2" × 11-1/2" | 191 × 292 | S4S | Large beams, girders |
| 10x10 | 9-1/2" × 9-1/2" | 241 × 241 | S4S | Large columns |
| 10x12 | 9-1/2" × 11-1/2" | 241 × 292 | S4S | Large beams |
| 12x12 | 11-1/2" × 11-1/2" | 292 × 292 | S4S | Very large columns |
| Grade | Description | Applications |
|---|---|---|
| Select Structural | Highest quality, minimal defects | Visible beams, heavy loads |
| No. 1 | High quality, minor defects allowed | Framing, general construction |
| No. 2 | Standard grade, moderate defects | Studs, joists, rafters |
| No. 3 | Utility grade, more defects | Sheathing, blocking |
| Stud Grade | Specific for wall framing | Wall studs |
| Construction Grade | Good quality, mixed use | General framing |