Earlier quoted context omitted.
There is square footage on many NYC listings, but it’s wrong. They often have the square footage of the total area occupied by the apartment, including all the interior walls and columns that can take 20% of the area away.
Don't forget about those common areas too! I've seen many cases where hallways, elevators, and stairwells were included in the square footage numbers.
Personally, I wish we would normalize including exact floor plans with measurements.