Quick Answer
2×4 in mm: 38 mm × 89 mm
A standard North American 2×4 (surfaced, kiln-dried) has an actual size of 38 mm × 89 mm.
In inches, that’s 1.5″ × 3.5″. The “2×4” name is nominal (rough-cut); the finished board is smaller.
Quick conversions
| Dimension | Millimeters | Centimeters | Inches |
|---|---|---|---|
| Thickness | 38 mm | 3.8 cm | 1.5″ |
| Width | 89 mm | 8.9 cm | 3.5″ |
Formula used: mm = inches × 25.4. (1.5 × 25.4 = 38.1 → 38 mm; 3.5 × 25.4 = 88.9 → 89 mm)
Why “2×4 in mm” isn’t 50 mm × 100 mm
The label “2×4” is the **nominal** (rough-sawn) name. After drying and surfacing, the **actual** size becomes 38 × 89 mm. In many metric markets, you’ll see products labeled by metric nominal sizes (e.g., 50 × 100), but U.S./Canada framing lumber finishes at **38 × 89 mm**.
Related sizes (in mm)
| Nominal | Actual (mm) | Actual (in) | Details |
|---|---|---|---|
| 2×4 | 38 × 89 | 1.5 × 3.5 | 2×4 actual size (home) |
| 2×6 | 38 × 140 | 1.5 × 5.5 | 2×6 actual size |
| 2×8 | 38 × 184 | 1.5 × 7.25 | 2×8 actual size |
| 2×10 | 38 × 235 | 1.5 × 9.25 | 2×10 actual size |
| 4×4 | 89 × 89 | 3.5 × 3.5 | 4×4 actual size |
FAQ: 2×4 in millimeters
What is a 2×4 in mm?
38 mm × 89 mm (actual finished size).
Is 2×4 the same as 50×100 mm?
No. 50×100 mm is a metric nominal. The U.S./Canada finished 2×4 measures 38×89 mm.
Do treated 2×4s in mm measure differently?
Finished size is the same (38×89 mm). Very wet treated boards may shrink slightly as they dry.