Quoted from pincoin:A 2x4 has always been 1 1/2 by 3 1/2, when they are rough cut from logs they are 2x4, when milled smooth is when you loose the 1/2 inch. Been that way for decades.
Don’t believe everything you read, a 2x4 use to actually be just that… a 2x4. I’ve been in carpentry many years and use to frame houses in the 90s, and I’ve remodeled a few older homes that had actual 2x4 construction.
The BS explanation is they start out 2x4 and are trimmed up to the current size (right, they trim off 25% of each board so they are straight and true… eye roll) This is completely false, especially in this day and age where precision instruments are used to maximize each log for lumber output.
A 2x4 hasn’t been a 2x4 for many decades now but its not because they trim off and throw away extra. It simply is due to more board production per log and more money generated.