A basic answer is length x width. It includes living area....the area should have heating, ventilation, natural light and livable. It would not include garages and basements.

I would call the city planer in your city and ask what the standard is for your community.

Matt,
Another good question. In Louisiana, we don't have basements. If you dig that far, you may find water! On every listing we are required to provide square footage. If it is not on record, we must measure the house. To measure a house you measure the exterior of the house, measuring jet outs and cut ins. If the house has a 2nd story we measure the interior of the rooms and make adjustments for the width of the walls. After you get all of your measurements, you deduct the garage and or workshop(if attached) and rooms that are not under the roof line or that are not heated and cooled. This would exclude an add-on such as a sun room that does not share the original roof line. If the porch was closed in and it was under the original roof line, it has vents added to heat and cool, it would be included. I guess there is a little difference depending on where you are. But that is how we figure sq. ft. when it is not provided. It is recommended that you measure all homes! An appraisal will include new measurements.

Thanks so much, Deborah. Your answer was very informative and I do believe that since this is an older home, it's just like you say - just the measurements of the rooms.

This varies slightly according to geography. I am not in NY, so please factor a margin for that in this answer.

Square feet would include everything above grade, and not a basement or attic. It would include hallways and bathrooms on the main floor. An appraiser generally measures the exterior of the main floor of the house as his/her starting point in determining square footage.

In some MLSs, a bedroom in a finished basement may not be counted in the total bedroom count. In other MLSs. such could be counted. I have heard of areas where finished basements that had a full walk-out could be included in the square footage for MLS purposes.

In NJ, many of our listings are absent a square footage count, because many of our homes are older. If the square footage is available from the tax assessor, agents will input that number. Calculaitons can vary slightly and for that reason, many agents will not provide a total square footage, but provide each individual room measurement.

An attic which has been completely finished for living space with permits can be counted as living space and included in the total square footage.