Quick Answer
2×4 Actual Measurement: 1.5″ × 3.5″ (38 mm × 89 mm)
The **actual measurement** of a standard 2×4 is 1.5 inches thick by 3.5 inches wide.
In metric terms, that’s 38 mm × 89 mm. Lengths (8′, 10′, 12′, etc.) vary by purchase.
Actual vs nominal
A “2×4” is the **nominal size**—its rough-sawn label. After kiln drying and planing smooth, material is removed, producing the **actual measurement** of 1.5″ × 3.5″.
Exact dimensions in all units
| Dimension | Inches | Millimeters | Centimeters |
|---|---|---|---|
| Thickness | 1.5″ | 38 | 3.8 |
| Width | 3.5″ | 89 | 8.9 |
Small variations occur from milling tolerances and wood moisture, but the standard spec is 1.5″ × 3.5″.
FAQ: 2×4 actual measurement
Is the actual measurement the same for treated 2×4s?
Yes—though wet treated boards can be slightly swollen until dry.
Do all U.S. 2×4s measure exactly 1.5″ × 3.5″?
Yes for surfaced (S4S) framing lumber, but slight acceptable variance exists.