2×4 Dimensions – Actual Size vs Nominal Size
Learn the real 2×4 dimensions, why they’re different from the name, and how to measure them accurately.
Quick Answer: A standard U.S. 2×4 measures 1.5 inches × 3.5 inches (38 mm × 89 mm) in actual size.
Nominal Size vs Actual Size
The term “2×4” refers to the nominal size, not the actual dimensions. Originally, a 2×4 was cut to exactly 2 inches by 4 inches. However, after drying and planing (smoothing the lumber), the size is reduced to the standard actual measurement used today.
2×4 Actual Dimensions
| Nominal Size | Actual Size (inches) | Actual Size (millimeters) |
|---|---|---|
| 2 × 4 | 1.5 × 3.5 in | 38 × 89 mm |
Why the Size is Different
The difference comes from the lumber milling process. A 2×4 is cut “green” (rough-cut) at the nominal size, then kiln-dried and planed to make the surfaces smooth. This finishing process removes material from each side, resulting in the smaller final size.
Common Uses for 2×4 Lumber
- Wall framing for houses
- Furniture building
- Workbenches and shelving
- General carpentry projects
Other Common Dimensional Lumber Sizes
| Nominal Size | Actual Size (inches) | Actual Size (millimeters) |
|---|---|---|
| 2 × 6 | 1.5 × 5.5 in | 38 × 140 mm |
| 2 × 8 | 1.5 × 7.25 in | 38 × 184 mm |
| 4 × 4 | 3.5 × 3.5 in | 89 × 89 mm |
Key Takeaways
- The “2×4” name refers to its nominal size, not the actual measurement.
- Actual size in the U.S. is 1.5 inches × 3.5 inches (38 mm × 89 mm).
- Differences are due to drying and planing during manufacturing.
- Knowing the true size helps ensure accurate cuts and fits in your projects.