Standard sizes of dimensional lumber include two-by-fours at 1 1/2 inches by 3 1/2 inches, two-by-eights at 1 1/2 inches by 7 1/4 inches and one-by-fours at 3/4 inches by 3 1/2 inches. Standard dimensional lumber is named according to its rough-cut size.
Standard lengths of lumber used for wall construction vary considerably depending on the height required, but are generally between 8 to 16 feet. Longer lengths are also manufactured by lumber mills but are not commonly stocked by most building-supply stores. Softwood lumber also comes in a number of standardized grades from 3 Common, for knotty wood, up to C Select, which contains almost no defects. The finished product is surfaced before it is sold, reducing its dimensions.