I find the room size published on hotel websites to be rather inaccurate, ie one hotel's 50sqm can be much bigger than the other. The perceived room size and how spacious it is to me will be influenced by number of furniture, how bulky they are and very critically, how much free space ( walkable space ) is in the room. One really has to see the room to be sure. Personally, I am kind of claustrophobic so anything less than 40sqm will not do and 50 - 60sqm is the norm. Preferably the room comes with high ceiling as well.