Common softwood sizes
These are the dry sizes from the American Softwood Lumber Standard. “Dry” means dried to 19% moisture or less. Undried (green) lumber is made slightly bigger.
| Nominal | Actual (inches) |
|---|---|
| 1 × 3 | ¾ × 2½ |
| 1 × 6 | ¾ × 5½ |
| 2 × 4 | 1½ × 3½ |
| 2 × 6 | 1½ × 5½ |
| 2 × 8 | 1½ × 7¼ |
A quick rule: a 1 inch nominal thickness is ¾ inch, and 2 inches is 1½. Widths up to 7 inches lose ½ inch. From 8 inches up they lose ¾ inch, so a 2 × 10 is 9¼ inches wide.
Always plan with the actual size. Three 1 × 6 boards laid side by side make a panel 16½ inches wide, not 18.
Hardwood quarters
Hardwood thickness is usually named in quarter inches of rough, unplaned wood. The USDA Wood Handbook gives these standard planed (surfaced two sides) thicknesses:
| Rough | Planed |
|---|---|
| 4/4 (1 in) | 13/16 in |
| 5/4 (1¼ in) | 1 1/16 in |
| 6/4 (1½ in) | 1 5/16 in |
| 8/4 (2 in) | 1¾ in |
See board foot for how these sizes affect the price.