Lumber Dimensions: Nominal vs. Actual
Dimensional Lumber
Lumber sizes can be confusing at first. Boards are referred to by their "Nominal Size", not the actual size. This is because lumber is surfaced or planed smooth on four sides (S4S). The nominal measurement is made before the lumber is surfaced. Always measure your lumber if precise measurements are needed.
Plywood and Sheet Goods
Sanding the panel during manufacturing, can remove up to 1/32 inch of material from the plywood sheet. So, for example, a plywood sheet with a thickness of 3/8 inch really has a thickness of 11/32 inch.
| Nominal Size | Actual Size |
|---|---|
| 1x2 | 3/4" x 1-1/2" |
| 1x3 | 3/4" x 2-1/2" |
| 1x4 | 3/4" x 3-1/2" |
| 1x6 | 3/4" x 5-1/2" |
| 1x8 | 3/4" x 7-1/4" |
| 1x10 | 3/4" x 9-1/4" |
| 1x12 | 3/4" x 11-1/4" |
| 2x2 | 1-1/2" x 1-1/2" |
| 2x3 | 1-1/2" x 2-1/2" |
| 2x4 | 1-1/2" x 3-1/2" |
| 2x6 | 1-1/2" x 5-1/2" |
| 2x8 | 1-1/2" x 7-1/4" |
| 2x10 | 1-1/2" x 9-1/4" |
| 2x12 | 1-1/2" x 11-1/4" |
| 4x4 | 3-1/2" x 3-1/2" |
| 4x6 | 3-1/2" x 5-1/2" |
| 6x6 | 5-1/2" x 5-1/2" |
| 5/4 x 6 | 1" x 5-1/2" |
| 6/4 x 6 | 1-5/16" x 5-1/2" |
| Nominal Size | Actual Size |
|---|---|
| 1/8 | 7/64 |
| 1/4 | 7/32 |
| 3/8 | 11/32 |
| 1/2 | 15/32 |
| 5/8 | 19/32 |
| 3/4 | 23/32 |