Lumber Sizes in Millimeters
Compare common U.S. lumber sizes with their approximate actual dimensions in millimeters.
Common Lumber Sizes in Millimeters
| Nominal Size | Actual Size (inches) | Approx. Metric Size |
|---|---|---|
| 2x2 | 1.5 × 1.5 in | 38 × 38 mm |
| 2x3 | 1.5 × 2.5 in | 38 × 64 mm |
| 2x4 | 1.5 × 3.5 in | 38 × 89 mm |
| 2x6 | 1.5 × 5.5 in | 38 × 140 mm |
| 2x8 | 1.5 × 7.25 in | 38 × 184 mm |
| 2x10 | 1.5 × 9.25 in | 38 × 235 mm |
| 2x12 | 1.5 × 11.25 in | 38 × 286 mm |
| 4x4 | 3.5 × 3.5 in | 89 × 89 mm |
| 4x6 | 3.5 × 5.5 in | 89 × 140 mm |
| 6x6 | 5.5 × 5.5 in | 140 × 140 mm |
How Are Lumber Sizes Converted to Millimeters?
The metric dimensions shown here are approximate conversions of the commonly referenced actual lumber dimensions.
For example, a 2x4 commonly measures about 1.5 × 3.5 inches. Converting those dimensions gives approximately 38 × 89 mm.
Metric values are rounded to practical whole-millimeter measurements and should not be treated as exact manufacturing specifications.
Why U.S. Lumber Uses Nominal Sizes
Common U.S. lumber is generally identified using nominal dimensions such as 2x4, 2x6, and 4x4. These names refer to nominal sizes rather than the final finished dimensions.
After drying and surfacing, the actual dimensions are smaller than the nominal dimensions.
Individual Lumber Sizes in Millimeters
Important Note About Metric Dimensions
Lumber dimensions can vary between products, grades, moisture conditions, manufacturers, and applicable standards. If a project requires a precise fit, check the actual dimensions of the specific lumber product.