The two-by-four is ubiquitous in construction. But the common wall stud may not measure up the way you would expect.
Carpenters, builders and homeowners rely on studs for consistent quality and dimensions. Stud is a term that describes a two-by-four in its common use. Similar terminology is applied to other softwood lumber types, such as one-by-four, two-by-six, four-by-four, four-by-six.
The origination of the term two-by-four is an old-school reference to rough lumber. The contemporary need to optimize for cost and efficiency has made the reference inaccurate -- studs are probably smaller than you think.
Even though it's called a two-by-four, the most common stud measures 1 1/2 by 3 1/2 inches. It has been run through machinery to smooth the face and round the corners, giving it consistent dimensions.
Even though dimensional lumber is supposed to be near perfect, don't be surprised -- if you decide to measure it -- that some studs range up to 1 5/8 inches in thickness. This shouldn't affect the lumber's use.
They're not used often, but the old-school, rough stud is exactly what the name implies; it's rough and fuzzy. It was cut from a tree and shipped. Because it has not been planed or run through a molder, it still has its original dimensions -- about 2 inches in thick and 4 inches wide, though these numbers are not always uniform.
Lumber charts are typically broken down into two categories. The first category is the "nominal" size, or rough size before the lumber is milled. The second category, "actual," is the size of the stud after it has been milled.
Beams, posts and almost all other softwood lumber is sized nominally. For example, the actual size of a standard two-by-six is 1 1/2 by 5 1/2 inches. The same goes for smaller pieces of lumber; the standard one-by-four measures only 3/4 by 3 1/2 inches.
Hardwood lumber has the same nominal and actual sizes, but the industry uses its own lingo. For example, a piece of oak that's 1 inch thick is refereed to as four-quarter, which is a nominal measurement. If it's 2 inches thick, it's referred to as eight-quarter.
Studs may occasionally be sized in decimals. The decimal equivalent of a common stud is 1.5 by 3.5 inches. If you have any questions about decimal equivalents, check the back side of your tape measure. Some manufactures include it.