There are several different "standards" for measuring square footage. Not everyone is on the same page for standardization. Not even the different appraisal organizations can agree on square footage standards. A general rule of thumb for square footage is to use the above grade living space but there are many "what if's" involved determining what may be a standard. Our local MLS, and many MLS's acress the country do not allow agents to enter square footage because of the variations between what the property valuation administrator, architect's plans and recent appraisals. In any situation only use the displayed square footage as a guide for determining what properties you may be interested in. ALWAYS verify the square footage for yourself, if square footage is important to you.