Wild. In Netherlands (and I assume other European countries as well) there’s a regulatory norm for how spaces should be measured - what counts as liveable, non-liveable, etc. It’s so much fairer and clearer for everyone involved.
https://www.nen.nl/bouw/beheer-en-onderhoud/oppervlaktebepal...
We largely have these regulations in the US too (at the state level), we just don't reuse them. Naturally there are rules about what is livable versus what is not. A balcony is not. A room with no windows isn't even a bedroom. That kind of stuff.
It would be truly trivial to then just transform that to calculating square footage, and many states do just that. But not all. It's a problem of motivation, not necessarily ability or cost.
Right? Germany too. I wouldn’t even have thought this could be a problem…
Back in the third world I remember my parents looked up the reference price per m^2 in the area and would divide the price by that to estimate the size.
Advertised amounts would be off by 20-25%. When you confronted them about it realtors would just give you the real number, I guess most people wouldn't go through the trouble so it was worth trying for them.