What are the actual dimensions of a board labeled as 2 x 4 after it has been surfaced and seasoned?

When a board is labeled as a 2 x 4, it refers to a rough cut dimension before the board is seasoned and surfaced. When the wood is processed—dried and planed to a smooth finish—it loses some thickness and width.

After surfacing, the standard actual dimensions of what is commonly called a "2 x 4" are 1-1/2 inches in thickness and 3-1/2 inches in width. This reduction occurs because the wood loses material during the milling process, as well as from moisture loss during drying, making the final sizing smaller than the nominal dimensions given.

Understanding these actual dimensions is crucial for contractors when framing and working with materials in construction projects, as accurate measurements impact structural integrity and fitting of components within the built environment.