The difference between “nominal” and “actual” dimensions for items like 2x4 dimensions
Nominal vs. Actual Lumber Dimensions
If you find reading plans and wood board sizes confusing or have trouble identifying the exact dimensions of wood at a lumberyard or home center, read on. Most lumber is sold in “nominal” (in name only) sizes. But these sizes are not the actual dimensions of the wood.
The chart below shows the actual dimensions of lumber when it is dry (when wet, it will be slightly larger). This handy chart will help you translate the nominal into the actual (dry). After a while, you’ll get the hang of dimensional lumber sizes.
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What Is Dimensional Lumber?
Dimensional lumber simply means that the lumber is pre-cut to standard sizes. You’re probably most familiar with the 2×4, but that’s not the only standard size out there. Other common sizes include 1×3, 2×6, 2×8 and 4×4.
If you’re building something (e.g a deck, framing a wall, etc) you’ll likely want to purchase dimensional lumber rather than spending the extra time getting it cut to size.
Dimensional Lumber Lengths
First of all, you need to know how to read lumber sizes. The first number is always thickness, followed by width. If you see a third number (e.g. 2x4x8), that number is length. Thickness and width are measured in inches, while length is measured in feet. So 2x4x8 is two inches thick by four inches wide, and the board itself is eight feet long.
Nominal vs. actual for wood with 2×4 dimensions
Wood dimension chart
This chart shows the nominal (in name only) and corresponding actual (real) dimensions of common wood sizes like 2×4 dimensions and 1×4 lumber.
Note: You can download and print the chart from Additional Information below.
