There is no information on an internationally average size.
400 square feet.
An average sized room such as a bedroom could be ten feet square or eight feet square. Larger rooms will be longer than they are wide.
324 square feet.
525 square feet.
120 square feet.
252 square feet.
130 square feet.
140 square feet.
352 square feet.
770 square feet.
300 square feet.
162 square feet.