Any measurement you add to a listing will be checked. If a buyer needs a loan, an appraiser will measure the home using the ANSI Z765-2021 standard, which Fannie Mae now requires for everyone. This guide covers what appraisers do, which tools give similar results, and where their methods differ from yours.
Tools Compared
| Tool | Will it match the appraisal | Turnaround | Cost | Use it for |
|---|---|---|---|---|
| Polycam | No, measures interior; gives an exterior total that runs closer | Minutes, on site | $400/yr per user, unlimited floorplans and reports | Listing plans, a working figure, and per-room areas |
| CubiCasa | No, measures interior | 24 hours, or 6 with rush | First 2D plan free, then per plan | A drafted plan without touching an editor |
| iGUIDE | No, measures interior | Quoted | Quoted, hardware required | Listings where the 360 tour is the product |
| Appraiser or measurement service | Yes, ANSI-compliant GLA | Days, by appointment | Per property | Any figure going in an MLS field or a dispute |
| Tax records | Unknown, county protocols vary | Instant | Free | Nothing, unless you cite the source in the listing |
The Appraiser Can No Longer Meet You Halfway
Following the rules is now a must. Fannie Mae says appraisers have to use the ANSI standard every time. There are no exceptions, and the old GXX001 code is no longer used. Appraisers also cannot adjust square footage to fit local habits, even if everyone else does it that way.
Reports now include more detail. The industry is switching from UAD 2.6 to UAD 3.6, along with a new Uniform Residential Appraisal Report. Fannie Mae now gives separate answers for each form, since the way you report things can differ.
Both of these changes have the same effect. Appraised values are now more consistent, and it is easier to see any difference between the appraiser’s number and your listing.
Two Correct Measurements Can Still Disagree
Knowing how the two methods differ lets you explain any differences to a seller before they become a problem.
ANSI measures from the outside surfaces of the walls, while your scan or tape measures the inside. The appraiser’s number includes wall thickness, but yours does not, and this difference adds up across the whole house.
Staircases are counted on the floor where they begin. In a two-story house, the stairs are counted once, on the upper floor.
Open spaces that look down to the floor below are not included. For example, a two-story foyer or a double-height living room is not counted twice, and the empty space is not counted at all.
Any area that is partly below ground counts as below grade. If any part of a floor’s walls is below ground level, the whole floor is below grade. For example, a walk-out basement with three sides underground is reported as below grade, no matter how well it is finished.
Low ceilings put space in a different category. Finished areas need a ceiling at least seven feet high. In rooms with sloped ceilings, at least half the area must reach seven feet, and no part can be lower than five feet. Space that does not meet these rules is listed as nonstandard finished area, so it appears in the report but not in the main total.
Condos are a common exception. ANSI doesn't apply to apartments or multifamily buildings. For these, Fannie Mae tells appraisers to measure the inside perimeter instead. So if you are listing a condo in one of these buildings, the appraiser measures it the same way you do, and there is no difference between exterior and interior measurements.
Fannie Mae Expects Your Floor Plan to Reach the Appraiser
Fannie Mae says that the growth of measurement apps is one reason for switching to a single standard. For desktop and hybrid appraisals, a floor plan is needed, but the appraiser does not visit the property, so the plan often comes from someone else.
The standard helps everyone stay on the same page. Software companies can follow it, agents know what to expect from appraisers, and appraisers can trust floor plans they did not create themselves.
A listing floor plan is not just for marketing. In a hybrid or desktop appraisal, it might be the document the appraiser uses, so how it was made is a professional issue, not just about presentation.
Which Tool for Which Job
For a listing plan and quick measurements, use a scan. Polycam lets you scan each room and gives you a floor plan with details like floor area, perimeter, ceiling height, and wall area for each room. It also provides both total exterior and total livable floor area for the property. Polycam Business and Enterprise subscribers can export the results in PDF, DXF, PNG, SVG, or CSV formats.
If you do not want to draft a plan yourself, CubiCasa can scan a property in about five minutes and send you a drafted plan within 24 hours, or in six hours with a rush order. The first 2D plan is free. This is a good option for occasional listings, but remember that any coverage issues may only show up after you have left.
If you want to offer a virtual tour, iGUIDE combines a floor plan with a 360-degree walkthrough using their own camera equipment. You will need to contact them directly for current pricing and turnaround times, since these are not published.
If you need your number to match the appraisal, order an ANSI measurement from an appraiser or a measurement service. This is the only way to get a figure calculated the same way the appraiser will.
Do not use tax records as your source unless you clearly say so. County methods vary. Some use ANSI, some do not. Fannie Mae notes that appraisers often cannot tell how an MLS or assessor figure was calculated.
What to Put in the Listing
Always say where your measurement came from. A number with a clear source is more reliable for both you and the buyer than one without any explanation.
Check your MLS rules before entering a measurement. Requirements vary by market, and some now require a specific measurement standard.
Explain the measurement process to the seller before the appraisal, not after. Fannie Mae’s guidance says that a consistent standard helps agents and lenders predict appraisal results, but this only works if you prepare ahead of time.
Keep a copy of the floor plan. If anyone questions your measurement, a dated plan that shows how you got the number is much better than relying on memory.
FAQ
Why is the appraiser’s square footage different from my listing?
ANSI Z765-2021 measures from the outside wall surfaces, so wall thickness is included. Your scan or tape measures the inside. Staircases count once, on the floor they start from. Openings to the floor below are not included, and anything partly below grade is reported as below-grade area.
Does ANSI apply to condos?
Not inside an apartment or multifamily building. Fannie Mae’s policy for a condo or co-op in that setting is to use interior perimeter measurement. ANSI does apply to condos in detached or attached houses, including townhouses and rowhouses.
What is UAD 3.6?
It is the updated Uniform Appraisal Dataset, adopted along with a redesigned Uniform Residential Appraisal Report. Fannie Mae’s measurement guidance now answers many questions separately for UAD 2.6 and UAD 3.6, because reporting practices differ between the forms.
Is a phone scan accurate enough for a listing?
For a working number and a plan buyers can read, yes. It measures the inside, so it will not match an ANSI figure, and you should not present it as an ANSI measurement.
Do finished attics and basements count?
A finished attic only counts if it meets the ceiling height rule, and any space that does not is reported separately as nonstandard finished area. Report any level partly below grade as below-grade area, not as part of the main figure.
