Making Sense of Lumber DimensionsUpdated: Jan. 18, 2023
The difference between “nominal” and “actual” dimensions for items like 2x4 dimensions
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Nominal vs. actual for wood with 2×4 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 such as 1×3, 2×4, 4×4 and2x2 lumber. But these sizes are not the actual 1×3 dimensions, 2×4 dimensions, 2×6 dimensions, 2×8 dimensions and 4×4 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 what 2 by 4 actual dimensions means, and it will help for projects like building a deck.