I would think that one would get the piano for the space, rather than the space for the piano? However...
As a starting point, my Steinway A is in a room which is about 17 feet by 30 feet by 9 feet (very roughly, 5.5 metres by 10 metres by 3 metres). It is, perhaps, a little big for the room. Some years ago I had my M in a somewhat smaller room, but one which opened onto a larger space (it now lives in a room about 20 feet by 20 feet, but with a ceiling also reaching almost 20 feet). However, keep in mind that a great deal can be done with the voicing of the piano to make it "fit" various spaces.
Even so, unless this is to be a real practice piano, also keep in mind that it is best if the audience -- if any -- needs to be a little distance to be comfortable; much closer than 10 feet away is probably too close for the sound to blend well at all.