It refers to pieces of wood used for building in North America, which comes in 2 inch by 4 inches by x feet, where x is generally 8 or 10.

So, basically a 50x100mm piece of lumber?

(I rounded those values because if the US were to go metric, the dimension would slightly change, rather than being exactly 50.8 by 101.6 mm)

Except, per my original point - it’s called a 2x4 - but it’s not actually 2 inches by 4 inches, which would be as you say 50ish x 100ish mm. In reality it’s actually standardized to be 38 x 89 mm

Guess 40 by 90 then.

What I tried to convey, in a stupid way, is that there wouldnt be an exact translation of the measurements into metric, but that the dimensions qould slightly change in switching over.

and now I realize that that point was irrelevant anyways. Sorry for derailing the thread with useless replies.

a north american measurement of wood