Lumber Dimensions

Have you ever noticed that a 4×4 isn’t really a 4×4? If you took out your tape measure you would find that a 4×4 is actually 3 ½” x 3 ½”. You’d also find that a 1×12 is actually a ¾” x 11 ¼”. So are the lumber companies trying to cheat you by making lumber sound larger then it is? No, you are not being cheated; there are actually U.S. standards that set what the actual dimensions are for each nominal dimension. I will go into more explanation of why dimensions are listed the way they are and will also provide a chart of the nominal vs actual measurements for your reference.

History of Lumber Dimensions

Lumber size standards started in the late 1800’s. With railroads creating distance between markets and lumber yards, it was important that standards existed so building materials were consistent.  As economic times got harder, lumber yards looked to reduce lumber costs, which could be done by shrinking the lumber dimensions. Today we see similar trends when packaged foods move to slightly smaller containers offering slightly less for the same price. These slightly smaller lumber dimensions have now become the U.S. standard, and a 4×4 is simply a name given to a specified piece of lumber. If you would like to know more about the history of lumber dimensions, take a look at the History of Yard Lumber Size Standards. Although written in 1964, the article gives a great in depth history of lumber dimensions and U.S. lumber standards.

What am I really getting?

Here is a chart courtesy of Wikipedia, which shows the nominal dimensions and the actual dimensions for standard lumber. Typically dimensions <2” are ¼” less than the nominal, dimensions <8” are ½” less than nominal, and dimensions ≥8” are ¾” less than the nominal.

I hope this was helpful and helped you to understand why a 4×4 isn’t really a 4×4. Feel free to leave any comments or questions below.


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