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What are the actual dimensions of a standard dressed 2 by 4?

About 1-1/2 by 3-1/2 inches.

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  1. 1-1/2 by 3-1/2 inches ✔
  2. 2 by 4 inches
  3. 1-3/4 by 3-3/4 inches

Why: Lumber is named by its rough, nominal size, then planed smooth. The dressed size is usually 1/2 to 3/4 inch smaller. So a 2 by 4 stud measures 1-1/2 by 3-1/2 inches.

Huh, didn't know that: The metric standard size for a 2 by 4 is 38 by 89 millimeters.

The dad joke
Why was the 2 by 4 embarrassed at the lumberyard? It was never as big as it claimed.
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References

Answer: 1-1/2 by 3-1/2 inches. Lumber is named by its rough, nominal size, then planed smooth. The dressed size is usually 1/2 to 3/4 inch smaller. So a 2 by 4 stud measures 1-1/2 by 3-1/2 inches.

  1. Wood Handbook: Wood as an Engineering Material, FPL-GTR-282 (USDA Forest Products Laboratory, 2021) research.fs.usda.gov/treesearch/62200
    A 2 by 4 in. stud, for example, actually measures about 1-1/2 by 3-1/2 in.
    Checked 2026-10-10.

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