Before the industrial era, all lumber was sawn and surfaced by hand. Boards were custom-milled to fit specific joinery, and sizes varied by region, mill, or carpenter. But in the 19th century, as sawmills became mechanized and railroads allowed for mass distribution, the need for standardization grew.
Enter dimensional lumber: standardized, mass-produced lumber with uniform nominal sizes for consistency across construction sites.
By the early 20th century, mills began surfacing rough-sawn boards to uniform thicknesses—leading to the familiar discrepancy between nominal and actual lumber sizes we still see today.
Nominal vs. Actual: What’s the Difference?
The nominal size refers to the lumber’s dimensions before drying and surfacing. The actual size reflects its final dimensions after the material is kiln-dried and planed smooth.
For example:
- A 2x4 starts out rough at 2″ x 4″
- After processing, it measures 1½″ x 3½″
This reduction is consistent for most softwood framing lumber.
Common Sizes and Their Actual Dimensions
| Nominal Size | Actual Size |
|---|---|
| 1x2 | ¾″ x 1½″ |
| 1x4 | ¾″ x 3½″ |
| 2x4 | 1½″ x 3½″ |
| 2x6 | 1½″ x 5½″ |
| 2x8 | 1½″ x 7¼″ |
| 2x10 | 1½″ x 9¼″ |
| 4x4 | 3½″ x 3½″ |
| 4x6 | 3½″ x 5½″ |
| 4x8 | 3½″ x 11¼″ |
Dimensional Lumber in Modern Woodworking
Dimensional lumber is the backbone of framing, cabinetry, trim work, shelving, and furniture construction. It’s prized for its affordability, accessibility, and predictable sizing.
Applications:
- Framing: 2x4s and 2x6s are used in wall and roof construction.
- Workbench building: 4x4s make great legs, while 2x12s serve as sturdy tops.
- Cabinetry face frames: 1x2s and 1x4s are often used for rails and stiles.
- Shelving and built-ins: 2x10s and 2x12s provide deep, supportive platforms.
For furniture builders, especially those using traditional joinery like mortise and tenon, understanding actual size is essential to fit and proportion.
Download the Free Dimensional Lumber Chart
To help you quickly identify and reference common lumber sizes, we've created a printable dimensional lumber chart with proportional visuals. It’s perfect for your shop wall, notebook, or job site clipboard.
Download the Dimensional Lumber Size Chart (PDF)
Final Thoughts
Understanding dimensional lumber is a foundational skill in both construction and fine woodworking. Knowing what you’re really working with saves time, reduces waste, and helps ensure your projects turn out exactly how you envisioned.
For more resources on woodworking techniques, joinery guides, and tool reviews, check out the rest of our blog.