Lumber Dimensions Chart
Actual vs nominal lumber size chart. Lumber is sold by “nominal” dimensions (e.g., 2x4) but the finished board is smaller after drying and planing.
Why Nominal ≠ Actual
Lumber is named by its rough-sawn dimensions before processing. After kiln-drying (which causes shrinkage) and planing smooth on all four sides, each dimension is reduced by approximately 1/2″ for boards under 2″ and 3/4″ for boards 2″ and larger. This is an industry-wide standard established in 1964.
| Nominal Size | Actual Size (inches) | Actual Size (mm) |
|---|---|---|
| 1 x 2 | 3/4" x 1-1/2" | 19 x 38 |
| 1 x 3 | 3/4" x 2-1/2" | 19 x 64 |
| 1 x 4 | 3/4" x 3-1/2" | 19 x 89 |
| 1 x 6 | 3/4" x 5-1/2" | 19 x 140 |
| 1 x 8 | 3/4" x 7-1/4" | 19 x 184 |
| 1 x 10 | 3/4" x 9-1/4" | 19 x 235 |
| 1 x 12 | 3/4" x 11-1/4" | 19 x 286 |
| 2 x 2 | 1-1/2" x 1-1/2" | 38 x 38 |
| 2 x 3 | 1-1/2" x 2-1/2" | 38 x 64 |
| 2 x 4 | 1-1/2" x 3-1/2" | 38 x 89 |
| 2 x 6 | 1-1/2" x 5-1/2" | 38 x 140 |
| 2 x 8 | 1-1/2" x 7-1/4" | 38 x 184 |
| 2 x 10 | 1-1/2" x 9-1/4" | 38 x 235 |
| 2 x 12 | 1-1/2" x 11-1/4" | 38 x 286 |
| 4 x 4 | 3-1/2" x 3-1/2" | 89 x 89 |
| 4 x 6 | 3-1/2" x 5-1/2" | 89 x 140 |
| 6 x 6 | 5-1/2" x 5-1/2" | 140 x 140 |
| 6 x 8 | 5-1/2" x 7-1/2" | 140 x 190 |
| 8 x 8 | 7-1/4" x 7-1/4" | 184 x 184 |
How to Read This Chart
Find the nominal lumber size you are working with in the left column. The middle and right columns show the real finished dimensions in inches and millimeters. Use these actual dimensions when planning cuts, designing furniture, or calculating material.
Frequently Asked Questions
Why is a 2x4 not actually 2 inches by 4 inches?
Lumber is named by its rough-sawn dimensions before drying and planing. After kiln drying (which shrinks the wood) and planing smooth on all four sides, the board loses about 1/2 inch in each dimension. A 2x4 starts as a rough 2" x 4" board and finishes at 1-1/2" x 3-1/2".
What is the actual size of a 2x6?
A nominal 2x6 has actual dimensions of 1-1/2 inches by 5-1/2 inches (38 mm x 140 mm).
When did lumber dimensions change from actual to nominal?
The current standard actual dimensions were formalized by the American Lumber Standard Committee in 1964 and have remained consistent since then.
Are pressure-treated lumber dimensions the same as regular lumber?
Yes. Pressure-treated lumber follows the same nominal-to-actual dimension standards. A pressure-treated 2x4 is still 1-1/2" x 3-1/2". The treatment process does not change the dimensions.