Common Lumber Sizes: Nominal vs. Actual Dimensions
One of the most common woodworking surprises is that the size printed on a lumber rack is not necessarily the finished dimension you can measure with a tape. Construction lumber is commonly sold using nominal sizes, while surfaced lumber is smaller after drying and milling.
Common examples
Typical finished dimensions vary by product, mill and market, so treat the table below as a planning reference rather than a promise of an exact size.
| Nominal | Common actual size (approx.) | Typical use |
|---|---|---|
| 1×4 | ¾ × 3½ in. | Trim, small parts |
| 1×6 | ¾ × 5½ in. | Panels, shelving |
| 2×4 | 1½ × 3½ in. | Framing, jigs |
| 2×6 | 1½ × 5½ in. | Framing, work surfaces |
| 2×8 | 1½ × 7¼ in. | Frames, benches |
| 2×10 | 1½ × 9¼ in. | Wide framing, larger projects |
Why it matters for calculations
If your cut list needs a finished panel that is 5½ inches wide, a nominal 1×6 may be a close match. But if you need exactly 6 inches of finished width, buying by the nominal label could lead to the wrong assumption. Enter the dimensions that actually describe the material you are buying or milling.
Before you buy
Measure a sample when the exact finished dimension matters, especially for reclaimed, surfaced or specialty lumber. Then use the Board Feet Calculator with the relevant dimensions.