A seller pulls up the county record and finds one number. The listing from when they bought the house says something larger. The appraisal comes back smaller than both. They ask which one is right, as though one of them has to be. Often none of them is wrong. They are measuring different things, under different rules, for different purposes.

The short answer

Square footage is not a single fact about a house. It is the output of whichever rule was applied. A mortgage appraisal is the one with a published standard behind it, and that standard is stricter than most sellers expect.

Where each number comes from

  • The county record exists for assessment. It is often built from exterior dimensions and permit history, and it is not re-measured every year.
  • An old listing reflects whatever the previous agent entered, from whatever source they had, under whatever the rules were then.
  • An appraisal is measured on site by a licensed appraiser, to a written standard, for a lender who is deciding how much to lend.

Those three are not competing attempts at one number. They are three separate errands.

The rule that governs the appraisal

For most conventional loans the appraiser measures to ANSI Z765-2021. Fannie Mae made that standard a requirement, so the rule is no longer a matter of local habit.

Source: Appraisal Institute, "Fannie Mae Adopts ANSI Standard for Square Footage Measurements," reporting the requirement as effective 1 April 2022 for appraisals involving interior and exterior inspections (Fannie Mae Selling Guide B4-1.3-05 and B4-1.2-01). Verified at source 14 September 2026.

What that standard actually counts

Two provisions surprise people more than any others. Ceiling height: finished area has to have a ceiling at least seven feet high. Where the ceiling slopes, at least half the finished area of the room must reach seven feet, and no part of it may be under five feet. Anything that fails those tests gets reported separately rather than counted with the rest.

And grade. Any level that is even partly below ground is reported as below grade area, not as part of the finished square footage above it. A floor counts as partly below grade if any portion of its walls is not entirely at or above ground level.

Source: Fannie Mae, "Standardized Property Measuring Guidelines" (singlefamily.fanniemae.com), on ceiling height, sloped ceilings and below grade reporting under ANSI Z765-2021. Verified at source 14 September 2026.

Which is why the basement is usually the argument

A finished lower level can be the best room in the house and still not appear in the number a lender uses. That is not the appraiser being difficult and it is not a statement about what the space is worth. Below grade area is reported, valued and disclosed. It is simply reported on its own line.

The uncomfortable version of this: a house marketed on a headline number that includes a walkout level will run into the appraisal eventually, usually about ten days before closing, when nobody has any room left to be flexible. It is a much easier conversation in week one.

Why I measure it before we price anything

I scan every listing myself, and I will tell you what the floor plan shows before we talk about a price. Scanning is part of taking a listing, every listing, every time, and it is never billed separately. The floor plan and the walkthrough are embedded in the MLS listing. The practical result is that the measurements come from the house rather than from a record somebody else typed, and the ceiling heights and grade changes that decide the number are visible before they become an argument.

The part I will not answer

Whether the county record should be corrected, and what that does to an assessment, is a question for the county assessor. Whether a measurement discrepancy affects a particular loan is the lender's answer and only the lender's. If a square footage figure is disputed after a closing, that is an attorney's question. I will tell you which of the three to call, and in what order, and I am not going to answer any of it myself.

What belongs to me is the house as it actually is: measured, drawn, and described the same way in every place a buyer will look.

How a house gets measured, drawn and marketed once it is ready is on the listing marketing page. If the question underneath this is whether to sell at all, the Lifestyle Calibration page is where that starts.

This note describes measurement standards in general terms. It is not an appraisal, not tax advice, and not a statement about any particular property. What governs your loan is the standard your lender and appraiser actually apply.