How Big? So Big.

Real Estate Agent with HomeSmart SA541769000

Tape Measure

Measuring the square footage of a house can sometimes be a mystery. Ask the seller how many square feet and you may get one answer. Ask the assessor how big, a second answer. Ask the appraiser and you may get even a different answer. Ask two appraisers and get two different answers.

Builders will often include square footage such as stairwells and utility closets in the living area. Assessors will often measure only the exterior perimeter of a building. Both may be incorrect when measuring for a residential appraisal.

How is square footage measured for appraisals? The unfortunate truth is that it depends on who’s measuring. The correct method for calculating the square footage of a home is determined by using the guidelines in ANSI standard Z765.

Many appraisers mistakenly round their measurements to the nearest foot. It makes the math easier, but it is improper procedure for an appraisal. Not all houses perfect squares. For houses with additions or cutouts, rounding to the nearest foot will impact the measurement. All dimensions of the house should be measured to the nearest inch or tenth of a foot; the final square footage is then reported to the nearest whole square foot.

ANSI Z765 also suggests measuring and multiplying the home’s exterior dimensions, then subtracting unfinished space, rooms that are not usable year-round, and rooms with a sloping ceiling that meet certain criteria.

Any inconsistencies to the measurement such as inability to access the property or utilizing builder plans should be noted on the appraisal.

Why is it important? Because a home’s value can often be influenced by how many square feet of living space is available. Let’s assume that properties in a given area sell on average for $250 per square foot. Adding or removing 100 square feet from a measurement can change the value by $25,000.

After viewing several appraisals on a single property it becomes clearer why the appraisal can often result in different numbers. Most often agents that run into issues with an appraisal find that it is because the appraiser used different comparable sales. But it may also be important to verify the square footage that the appraiser is using to value the property. It may make a difference.




Joe Domino is a Realtor® serving the Phoenix & Scottsdale metro area. You can find more great information by visiting his website at




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Susan Hale
Re/Max Realty of Defiance,Inc. - Defiance, OH
Re/Max Northwest Ohio Realtor

Great topic, Joseph.  My broker says go by the courthouse records square footage. Our MLS has a checkbox as to sq footage source.   If seller says it is more make a notation in the agent remarks area that the Seller questions the court house  square footage amount and by what amount.  Note: Sellers may have finished an enclosed porch area with heat runs, drywall and flooring without getting building permits and the courthouse doesn't have that extra data at this time,etc. 

I've heard you can't include basement sq footage unless it is a walkout basement with daylight windows and then only the finished rooms?  There are so many interpretations...

Nov 22, 2019 07:54 AM #1
Michele Cadogan 917-861-9166
Fillmore Real Estate 2990 Av U, Bklyn , NY 11229 - Brooklyn, NY
Licensed Real Estate Associate Broker -

Bookmarked to revisit - this maybe something somthing to share with  a home owner  appealing their  property tax ssessment. 

Nov 22, 2019 07:59 AM #2
Carol Williams
Although I'm retired, I love sharing my knowledge and learning from other real estate industry professionals. - Wenatchee, WA
Retired Agent / Broker / Property Manager

Hi Joseph,
Excellent points! I think analyzing the value of a home by an average per square foot is ok for a ballpark figure but it can't be the main factor. There are soooo many other factors, aren't there? 

Nov 22, 2019 03:19 PM #3
Nina Hollander
Coldwell Banker Residential Brokerage - Charlotte, NC
Your Charlotte/Ballantyne/Waxhaw/Fort Mill Realtor

Hi Joseph... I decided immediately upon getting my license to never measure a home myself. I have always hired a professional who measure to North Carolina rules for our MLS... and thankfully have not in 21 years ever had a problem.


Nov 23, 2019 04:24 AM #4
Michael Jacobs
Pasadena, CA
Los Angeles Pasadena 818.516.4393

Hello Joseph - "tools" of all kinds and I are not a good match.  That includes a tape measure.  As far as determing square footage of a property, the methods/sources are abundant.  Cite the source.  2108 square feet per tax assessor records or whatever number you use.  Proper disclosure is key.  

Nov 23, 2019 05:54 AM #5
Sheila Anderson
Referral Group Incorporated - East Brunswick, NJ
The Real Estate Whisperer Who Listens 732-715-1133

Good morning Joseph. I think this is excellent and explains a great deal.

Nov 23, 2019 06:12 AM #6
Debb Janes EcoBroker and Bernie Stea JD
ViewHomes of Clark County - Nature As Neighbors - Camas, WA
REALTORS® in Clark County, WA

Great discussion Joe. We also disclose our source in listings and generally have a blue print showing the dimensions of all the rooms. The real bug-a-boo can be those daylight basements where some rooms may not qualify as legitimate square footage. 

Nov 23, 2019 07:24 AM #7
Jeff Dowler, CRS
Solutions Real Estate - Carlsbad, CA
The Southern California Relocation Dude

Hi Joseph:

This is a good discussion and you've raised some great points. Square footage can often be in dispute and there have been lawsuits over discrepancies. The other issue that sometimes comes along is the SF of unpermitted space.


Nov 23, 2019 11:50 AM #8
Anna Banana Kruchten Broker/Owner, CRB, CRS
Phoenix Property Shoppe - Phoenix, AZ

Hi Joseph many years ago in AZ square footage became a big legal issue so the rules were changed to avoid lawsuits regarding source of square feet. It's so important for agents not to be the source. County or appraiser and if seller doesn't agree, then as you mentioned put in in the remarks as to what seller thinks it is different from county records.  Albeit....for sellers not to get permits for added square footage is counter productive in the long run.

Nov 23, 2019 01:46 PM #9
Tom Bailey
Margaret Rudd & Associates Inc. - Oak Island, NC

Thanks for the post Joe! I don't measure houses! I have always hired a reputable appraiser 

Nov 23, 2019 02:15 PM #10
MichelleCherie Carr Crowe Just Call...408-252-8900
Get Results Team...Just Call (408) 252-8900! . DRE #00901962 . Licensed to Sell since 1985 . Altas Realty - San Jose, CA
Family Helping Families Buy & Sell Homes 40+ Years

There is a lot of variation in appraisals and not just in how they measure the square footage

Nov 24, 2019 06:37 PM #11
Mary Hutchison, SRES, ABR
Better Homes and Gardens Real Estate-Kansas City Homes - Kansas City, MO
Experienced Agent in Kansas City Metro area

I wonder how appraisals do their calculations...always thought it was based on living space--so an attached garage doesn't count in the SF.  As well as an unfinished basement. Next time I meet an appraiser, will ask !

Dec 02, 2019 10:43 AM #12
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