ANSI Square Footage Calculator
Under ANSI Z765-2021, finished above-grade area, the number appraisers used to call gross living area, is finished space entirely above ground with ceilings of at least 7 feet (a sloped room counts down to the 5 foot line if at least half of it reaches 7 feet). Basements, low or mostly sloped rooms, rooms you can reach only through unfinished space, garages and openings to the floor below are reported separately or not at all. Enter each area of the house below and the calculator sorts it into the six lines Fannie Mae and Freddie Mac's UAD 3.6 appraisal reports use, rounded to the whole square foot.
One entry per area that's measured as a rectangle: a level, a wing, a room
with a different ceiling. Lengths in feet: 28.5, 28 6 or 28'6".
Stairs belong to the level they come down from. The example is Fannie Mae and Freddie Mac's own:
a 1,500 sq ft main level, a 400 sq ft garage, and an upper level with a sloped-ceiling office.
Interior room sizes leave out the walls, so their totals come out smaller than a measurement of the house's outside.
A finished room you can reach only through the garage or from outside is what the job aid calls noncontinuous, and it isn't one of the six lines: leave it out here and tell the appraiser.
Enter an area's length and width to see the breakdown.
The rules the calculator applies
The standard itself is sold by Home Innovation Research Labs. These are the rules Fannie Mae lists for appraisers in its ANSI fact sheet and FAQ (March 2022), and the area lines are from Fannie Mae and Freddie Mac's UAD 3.6 ANSI job aid (June 23, 2026):
- Precision. Measurements are taken to the nearest inch or tenth of a foot, and the final square footage is reported to the nearest whole square foot. The calculator keeps every area exact and rounds each total once.
- Below grade. A basement is any space partially or completely below grade, and a level is partially below grade if any portion of its walls is not entirely at or above ground. On that rule, a walkout lower level with earth against any part of its walls is below grade (our reading).
- Ceiling height. Finished area needs a ceiling of at least 7 feet. In a room with a sloping ceiling, at least 50% of the room's finished area must be 7 feet or higher, and no part under 5 feet counts.
- Stairs and openings. Stairs count on the level they descend from. Openings to the floor below, such as a two-story foyer, don't count.
- Nonstandard finished area. The job aid's term for finished space with direct interior access that doesn't meet the ceiling rules, or that's reached through unfinished space such as an unfinished hallway, room or staircase. It's reported on its own line, above or below grade.
- Garages and ADUs. An attached garage is on none of the six lines. An accessory dwelling unit gets its own area breakdown, separate from the house's.
Fannie Mae and Freddie Mac's examples, run through the calculator
The job aid works nine houses through to the numbers an appraiser enters. These are the ones that turn on a rule, and the calculator reproduces each:
| House | What's measured | Result |
|---|---|---|
| Example 1: one level | 45.3 × 28.5 ft, plus a 20 × 20 ft garage | 1,291 sq ft finished above grade; the garage isn't on any line |
| Example 5: partly finished basement | Main level 1,500 sq ft; basement 40 × 30 ft finished, 10 × 30 ft unfinished | 1,500 above; 1,200 finished below grade; 300 unfinished below grade |
| Example 6: low basement ceiling | Basement 30 × 30 ft at 7 ft or more, 20 × 30 ft between 5 and 7 ft | 900 finished below grade; 600 finished below grade (nonstandard) |
| Example 7: sloped upper level | Upper level 1,000 sq ft to the 5 ft line, 400 of it at 7 ft or more | All 1,000 nonstandard: 400 is under half |
| Example 9: one sloped room | Main 50 × 30 ft; upper 30 × 20 ft at 7 ft or more, plus a 20 × 14 ft office with walls at 5 ft and a 7 ft peak | 2,100 finished above grade; 280 nonstandard |
Example 9 is the one to remember on a shoot. The office is finished and used as a room, and its ceiling never drops below 5 feet, but because less than half of it reaches 7 feet, it isn't part of the finished above-grade total. A listing that adds the office in and says 2,380 square feet, and an appraisal that says 2,100, can be describing the same house.
Why this matters if you shoot floor plans
Fannie Mae requires ANSI Z765-2021 for appraisals with interior and exterior inspections, with effective dates on or after April 1, 2022, on loans it buys. In its FAQ it says one reason it adopted the standard was phone apps that measure houses, generate floor plans and calculate living area, and it calls ANSI a standard "other parties (such as real estate agents) can anticipate." Its FAQ also says the square footage in MLS listings and assessor records may not follow ANSI, and that ANSI lets agents and others "better anticipate appraisal outcomes, which can help reduce loan closing issues." When your floor plan's numbers end up on the listing, that's the gap they can close or open.
The UAD 3.6 mandate date is November 2, 2026, per Freddie Mac. UAD 3.6 appraisal reports show the area breakdown above instead of a single gross living area figure. A floor plan that labels its areas the same way, finished above grade, finished below grade and the rest, saves the agent a surprise.
Where Fannie Mae doesn't use it: the standard doesn't apply to 2- to 4-unit dwellings, shouldn't be used for condos and co-ops in an apartment-style or multifamily building (those use interior perimeter measurements; townhouses and rowhouses do follow ANSI), and isn't required for outbuildings (ADUs must follow it) or desktop appraisals, where it's encouraged. Appraisers can also take an exception, for example for a berm home with all of its area below grade or in a state that requires a different measuring standard.
What to put on the floor plan
If you publish square footage at all, give the breakdown, not one number: the agent can see what's above grade and what isn't, and choose what goes in the listing. Keep the label honest. Nobody certifies a measurement under ANSI. For appraisers, Fannie Mae says the standard requires written declarations and that failing to provide them voids any claim of adherence, so "measured per ANSI Z765-2021" is a claim that comes with paperwork. "Grouped by ANSI Z765 area type, from on-site measurements, approximate" is accurate, and it's what the calculator's summary says. Our guide to floor plans for real estate listings covers capture, pricing and the liability side.
Frequently asked questions
Does a basement count as square footage under ANSI Z765?
Not as above-grade finished area. Under the standard a basement is any level that is partially or completely below grade, and Fannie Mae counts a level as partially below grade if any portion of its walls is not entirely at or above ground level, so on our reading a walkout lower level is below grade too. A finished basement is reported on its own line, finished below grade.
How do sloped ceilings count in ANSI square footage?
Floor under a ceiling lower than 5 feet doesn't count at all. For the rest of the room, at least half of it must have a ceiling of 7 feet or more. If it does, the whole room down to the 5 foot line counts as finished area. If it doesn't, the room is reported as nonstandard finished area instead. In Fannie Mae and Freddie Mac's own example, a 1,000 square foot upper level with 400 square feet at 7 feet or more is all nonstandard.
Do stairs and garages count in ANSI square footage?
Stairs count, on the level they come down from. A two-story foyer or other opening to the floor below doesn't count on the upper level. A garage isn't finished or unfinished living area: in Fannie Mae and Freddie Mac's examples, an attached 400 square foot garage is left out of all six area lines.
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