How to figure out square footage?

The correct way to calculate sq ft is from inside of outside walls, excluding unfinished space, since that's livable sq ft. Measuring from outside of outside walls is kind of a joke since walls can be 6 inches - 2 feet thick (bigger issue in NYC) - including unfinished sq ft is also a joke. But the reality is every broker out there tries to quote the highest possible sq ft so if you're trying to do comps then you either need to go measure the comps (which will probably be impossible) or just use the same screwed up methodology so you're comparing similar $ / sq ft.

Agree with nyc 10013. $./sq.foot is never sn exact science-there is no substitute for viewing the place and using your own judgement.

Thanks to both of you for answering - your responses are in alignment with what made sense to me, but you know how it is our there...