Nope. They used to average 2 real inches by 4 real inches. The studs in the 100 year old section of my house are that dimension. 1.5” x 3.5” was the lower end of the tolerance level for old sawmill technology. They couldn’t cut as accurately as we can now, so anything between that lower limit and 2.5”x4.5” could be called and understood within the trade to be a 2x4.
As sawmill technology improved, they took the industry standard — a 2x4 is anything between 1.5” and 2.5” thick + 3.5” and 4.5” wide — and set all the tolerances at the extreme low end. This results in us getting perfectly uniform boards so the architects know exactly what they will do, and the sawmills get more useful boards out of the same tree.
As sawmill technology improved, they took the industry standard — a 2x4 is anything between 1.5” and 2.5” thick + 3.5” and 4.5” wide — and set all the tolerances at the extreme low end. This results in us getting perfectly uniform boards so the architects know exactly what they will do, and the sawmills get more useful boards out of the same tree.
Wrongo! That is not how they came to the designation of 2x4. The 2x4 is unfinished wood, 2 inches by 4 inches. It is smoothed in the milling process by shaving of about 1/4 inch from each face, creating finished lumber. Thus, a 2x4 is 1.5x3.5, and a 2x6 is 1.5x5.5 and a 4x8 is 3.5x7.5. And I didn't look it up on Wikipedia.