# I am unclear as to how square footage is determined. I compare listings, look at the sizes of the rooms and the number of beds and baths and often the

Asked by Geo, Chicago, IL Wed Oct 7, 2009

numbers just don&#039;t add up. How are these numbers determined? And how can I educate myself as a buyer when it comes to determining value based on size?

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The tax assessor's office is often the most popular source for square footage information when determining the buildings square footage of a property however often this information is inaccurate, especially if the property was added on to over the years. In addition square footage that is below grade, as in the basement, even if finished is technically not supposed to be counted as livable square footage for purposes of tracking in the MLS, even though some agents and home owners will include. That being said, I find it is always helpful when compiling CMAs for my clients, to put together a spread sheet to include room count and size, along with lot size.....to get a more accurate assessment of the properties true square footage costs...which for the record in Wilmette right now is running around \$344 a square foot up 6% from a year ago per Trulia's market trends information.
I agree with everything that Patrick said regarding square footage, but would add that I believe the best number to mutiply the sum of the room sizes by is 1.5, especially for older homes. I base this upon 16 years of doing square footage calculations and speaking with appraisers. 1.3 may work okay for homes with little hallway and closet space suck as homes constructed in the 1950's, but for homes that have significant hallway and closet space, I believe 1.5 generally gives a closer approximation. But as Patrick notes, the only way to get real precise on the square footage is to measure the outside perimeter if the home or to get it from a survey.

John Nash
http://www.JohnNashHomes.com
Art is 1/2 correct, square footage is but one of many factors that typically correlate to sale price. However it is not irrelevant. We value properties using multiple linear regression analysis and there is always a strong correlation between above ground square footage and sale price.

Whether you use the tax assessors numbers or add up the rooms and multiply by 1.3 (a fair estimate) their will be inconsistencies. This is why you need a large data sample; making a one to one comparison will be highly vulnerable to false correlations.
Web Reference: http://www.realtyfreak.com
George,
Most homes listed in the MLS for Wilmette don't even include the square footage. Condition, location, lot size and age are more important and make comparing homes on the basis of square footage a waste of time. Find a home you like based on these other criteria and you'll be much happier in the end.
Calculating the square footage of a home is not an exact science. Usually the tax assessors office with have the square footage but many times it is not accurate do to additions and floor plan changes. Some will take the room sizes and factor in a formula to come up with square footage. Some will measure from the outside walls to get square footage. This method will include hallways and staircases. More detailed methods will remove the non living spaces Square footage is usually the livable space that is heated by conventional methods, finished space and above ground living. Basements usually don't factor in to the square footage.

To get a ball park idea, measure all the rooms and multiply each each room length x width to get the square footage of each room. Add all the room sizes together then multiply by 1.3. This will factor in the spaces such as halls and bathrooms. The result will give you the approximate square footage.

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