Guide
ANSI Z765-2021: The Square Footage Rules Explained
What ANSI Z765-2021 says about finished area, ceiling height, below-grade space, garages, stairs and openings, and how to report square footage under it.
Updated · FloorFigures
Short answer
ANSI Z765-2021 is the American National Standard for measuring single-family houses, published by Home Innovation Research Labs. Measure each level to the exterior finished surface of the outside walls, count only finished area with ceilings of 7 ft or more, report above-grade and below-grade area separately, leave out garages, porches and openings to the floor below, and round to the whole square foot. Fannie Mae has required it for appraisals since April 1, 2022, and Freddie Mac since November 2, 2023.
Most square footage disputes come down to one question: measured how? ANSI Z765 is the closest thing the US has to a single answer for houses. It is short (16 pages), and its rules fit on one screen. The details below are what appraisers, builders and careful agents actually apply, rule by rule, with the official sources at the end.
What counts and what doesn't: quick reference
| Area | Counts? | How it's handled |
|---|---|---|
| Finished rooms on a level entirely above grade, 7 ft+ ceilings | Yes | Above-grade finished area (what appraisers call GLA) |
| Finished basement or walkout level | Yes, separately | Below-grade finished area, never added to above-grade |
| Garage, even finished or heated | No | May be reported as unfinished area |
| Wall between the house and the garage | Yes | Measure to the gypsum surface on the garage side |
| Open porch, deck, balcony | No | May be listed separately, measured to the outer edge |
| Enclosed porch or sunroom finished like the house, usable year-round | Yes | Finished area on its level |
| Two-story foyer or great room, upper level | No | Counted once, on the floor it sits on |
| Stairs and landings | Yes | On the floor they descend from, up to the size of the opening |
| Ceiling under 7 ft (6 ft 4 in under beams and ducts) | No | Fannie Mae: report as nonstandard finished area |
| Sloped ceiling | Partly | Room counts if at least half is 7 ft+; nothing under 5 ft counts |
| Finished room reached only through unfinished space | No | May be listed separately |
| Chimney or bay window with no floor at that level | No | A floor-to-ceiling window with floor counts |
| Bare or painted concrete floor | No | Not a finish; decoratively finished concrete is |
What is ANSI Z765?
ANSI Z765, Square Footage: Method for Calculating, is an American National Standard for measuring, calculating and reporting the square footage of single-family houses. It is published by Home Innovation Research Labs, an independent subsidiary of the National Association of Home Builders (NAHB). Home Innovation was called the NAHB Research Center until it was renamed on February 12, 2013. The electronic copy of the 2021 edition costs $25.00 from the publisher's store.
| Edition | Status |
|---|---|
| 1996 | First adopted |
| 2003 | Revised |
| 2003 (R2013) | Reaffirmed in 2013 with the same text |
| 2021 | Approved April 2021; current. Next review due no later than 2028 |
ANSI Z765 is not a law. In its own words, it is "not meant to replace or supersede any legal or otherwise required existing area measurement method." It becomes binding when someone adopts it, as Fannie Mae and Freddie Mac have for appraisals.
What does ANSI Z765 cover?
- Detached and attached single-family houses: detached homes, townhouses and rowhouses.
- Not apartments or multifamily buildings. Condo and co-op apartment units are measured another way (Fannie Mae uses interior perimeter measurements for them).
- Not room dimensions. It measures the house and its levels, not individual rooms.
- All or nothing. The standard "must be applied as a whole". You can't follow the parts you like and still claim to use it.
Key definitions
- Finished area: an enclosed area "suitable for year-round use", with walls, floors and ceilings "similar to the rest of the house". Bare or painted concrete is not a floor finish; decoratively finished concrete is.
- Level: areas "vertically within 2 ft of the same horizontal plane". In a split-level house, floors less than 2 ft apart are one level.
- Grade: the ground level at the perimeter of the exterior finished surface of the house.
The measuring rules, one by one
Measure to the exterior finished surface
A detached house is measured level by level, "at floor level to the exterior finished surface of the outside walls": the face of the siding, brick or stucco, not the foundation or the inside of the drywall. An attached house (a townhouse or rowhouse) is measured to the exterior finished surface, or "from the centerlines between houses, where appropriate". Because ANSI measures the outside, room sizes printed on a plan add up to less than the house total. That gap is the walls, halls and closets, not an error.
Where finished meets unfinished, and the garage wall
When finished space sits next to unfinished space inside the house, measure the finished area to the exterior edge of the partition: the unfinished side. At a garage wall, measure to the gypsum surface on the garage side, so the whole shared wall belongs to the finished area.
Rounding
Take measurements to the nearest inch or tenth of a foot (0.01 m in metric) and report finished square footage to the nearest whole square foot (0.1 m²). Round the total, not each piece: 40.5 ft × 30.2 ft is 1,223.1 sq ft, which you carry into the sum and round once at the end.
Ceiling height
Finished area needs a ceiling of at least 7 ft (2.13 m). Under beams, ducts and other obstructions, 6 ft 4 in (1.93 m) is enough. Stairs have no height requirement. A finished room with a flat 6 ft 10 in ceiling is not finished square footage under ANSI. Fannie Mae has appraisers report it as nonstandard finished area instead. More in ceiling height rules.
Sloped ceilings
In a room with a sloped ceiling, at least half of the room's finished square footage must have a ceiling of 7 ft or more. If it does, the room counts, including the parts between 5 ft and 7 ft. No area with a ceiling under 5 ft (1.52 m) is ever counted. If less than half the room reaches 7 ft, the room doesn't count as finished square footage at all.
| Band | Width × length | Area | Counted |
|---|---|---|---|
| 7 ft or higher | 16 × 15 | 240 sq ft | 240 sq ft |
| 5 ft to 7 ft | 4 × 15 (2 ft each side) | 60 sq ft | 60 sq ft |
| Under 5 ft | 4 × 15 (2 ft each side) | 60 sq ft | 0 |
| Room | 24 × 15 | 360 sq ft | 300 sq ft |
Above grade and below grade
Above-grade area is on levels entirely above grade. Below-grade area is on levels wholly or partly below grade. So if any part of a level is below grade, the whole level is a below-grade level, including a walkout basement with a full wall of windows. Some houses (a berm home built into a hill, for example) have no above-grade square footage at all. Fannie Mae puts it this way: a level is partially below grade "if any portion of its walls is not entirely at or above ground level." See does a basement count.
Openings to the floor below
Two-story foyers, great rooms and other openings to the floor below are excluded from the upper level. The space counts once, on the floor it sits on. See open to below.
Stairs
- Stair treads and landings count on the floor from which they descend, but not more than the area of the floor opening.
- Stairs down to an unfinished basement count as finished area of the level above, whatever their finish.
- The area beneath stairs counts in the lower level's finished area, regardless of headroom or finish.
In practice: don't subtract the stairwell opening on the upper floor. More in how stairs are counted.
Connected areas
Finished areas connected to the house by finished hallways or stairs count on the level they sit on. Finished areas that aren't connected that way "cannot be included in the finished square footage of any level", though you may list them separately. The classic case is a finished room over the garage: it counts only if there is a continuous finished connection to the rest of the house. If you reach it through the garage, it doesn't. Fannie Mae calls areas reached through unfinished space nonstandard finished area and requires appraisers to report them separately.
Garages
A garage is never finished area, however it is finished or heated. It may be reported as unfinished area (follow local custom). See does a garage count.
Porches, balconies and decks
Porches, balconies and decks that aren't enclosed and suitable for year-round use are excluded. You may list them separately, measured from the exterior finished surface of the house to their outer edge.
Chimneys, bay windows and other protrusions
Chimneys and bay windows that have no floor at that level are excluded. A floor-to-ceiling window, which has a floor, is included.
How do you report square footage under ANSI Z765?
Never as one number. The standard doesn't allow a statement of finished square footage that doesn't separate the above-grade and below-grade figures. A compliant statement reads like "Above-grade finished area: 2,452 sq ft. Below-grade finished area: 725 sq ft."
A declaration is also required when the figures come from anything less than a full measurement:
| Declaration | When it's required |
|---|---|
| Declaration 1 | The house was measured from the outside only and the interior wasn't inspected |
| Declaration 2 | The figures were calculated from plans |
| Declaration 3 | The figures rest on estimated dimensions |
Declaration 2, the one that applies whenever you measure a floor plan, reads:
"Finished square footage calculations for this house were made based on plan dimensions only and may vary from the finished square footage of the house as built."
Leaving out a required declaration "voids any claim of adherence" to the standard. Fannie Mae, for its part, doesn't require an affirmative statement that ANSI was followed, but since its June 2025 update it expects full compliance, declarations included.
What changed in ANSI Z765-2021 from 2003?
Not much in substance. The publisher says the 2021 revision "did not fundamentally change the standard". The main changes were clarifications in the commentary:
- Stairs to unfinished areas: clearer guidance on stairs that lead to unfinished areas.
- Sloped ceilings: a clarified figure for the half-at-7-ft rule.
The ceiling heights (7 ft, 6 ft 4 in, 5 ft), the below-grade rule, the garage and porch exclusions and the declarations carry over from 2003. The publisher's 2020 public drafts also show reorganized, numbered sections and some wording changes; if you need exact 2021 wording, buy the final text from Home Innovation.
Who requires ANSI Z765?
| Who | Rule | From | Applies to |
|---|---|---|---|
| Fannie Mae | Selling Guide B4-1.3-05 | Appraisals effective on or after April 1, 2022 | Hybrid appraisals and appraisals with interior and exterior inspections; not condo or co-op units or 2–4 unit properties |
| Freddie Mac | Bulletin 2023-15 | Appraisals effective on or after Nov 2, 2023 | 1-unit properties, excluding apartment-style condo and co-op units |
| Fannie Mae desktop appraisals | Selling Guide B4-1.2-02 | Current | Not required, but encouraged when feasible |
| UAD 3.6 (redesigned URAR) | Fannie Mae and Freddie Mac | Reports first submitted to UCDP on or after Nov 2, 2026 | Six ANSI-based area fields replace the single GLA figure |
Fannie Mae also says that when appraisers use sketching or 3D scanning software, "the resulting output must conform to the ANSI standard." Details in Fannie Mae's ANSI requirement and UAD 3.6 and square footage.
Outside appraisals, ANSI is voluntary. There is no single US legal standard for listing square footage, though the National Association of REALTORS® notes that several states require appraisers to comply with ANSI, and some state real estate commissions publish guidelines built on the same ideas (North Carolina's use the same 7 ft, 6 ft 4 in and sloped-ceiling rules). See who's responsible for listing square footage.
Applying ANSI Z765 to a floor plan
FloorFigures applies these rules when you measure a plan, and it's free. Overlapping areas are merged so nothing is counted twice; garage, porch, deck and unfinished areas are carved out of living area; openings to below are subtracted; the ceiling-height rules (7 ft, sloped rooms, nothing under 5 ft) are applied; finished space on below-grade levels is reported as below-grade finished area; and totals are rounded to the whole square foot, with a statement you can copy into a report. Because the figures come from a plan, add Declaration 2. To check a figure without a plan, use the ANSI Z765 GLA calculator, or follow the step-by-step GLA example.
Official sources
- Home Innovation Research Labs, ANSI Z765 overview and store (2021 edition, $25.00, 16 pages).
- Home Innovation, consensus committee approves the latest version (2021 edition announcement).
- ANSI Z765-2003 text (PDF, hosted by UBC Sauder School of Business).
- ANSI Z765 public draft, February 2020 (PDF, Home Innovation).
- Fannie Mae Selling Guide B4-1.3-05 (measuring requirement) and B4-1.2-02 (desktop appraisals).
- Fannie Mae, Standardized Property Measuring Guidelines FAQ (July 2022, PDF copy).
- Freddie Mac Bulletin 2023-15 (July 2023).
- Fannie Mae and Freddie Mac, UAD ANSI Reporting Requirements job aid (June 23, 2026, PDF).
Questions
- What is ANSI Z765?
- ANSI Z765 is the American National Standard for measuring and calculating the square footage of single-family houses, detached and attached. It is published by Home Innovation Research Labs, and the current edition is ANSI Z765-2021. It says to measure each level to the exterior finished surface of the outside walls, count only finished area, report above-grade and below-grade area separately, and round the result to the whole square foot.
- Is ANSI Z765 required by law?
- No. ANSI Z765 is a voluntary consensus standard, and the standard itself says it is not meant to replace any legal or otherwise required measurement method. It becomes mandatory through the people who adopt it: Fannie Mae has required it for appraisals since April 1, 2022 and Freddie Mac since November 2, 2023, and some states require appraisers to use it. Listing square footage has no single national legal standard.
- What is the minimum ceiling height under ANSI Z765?
- 7 ft. Finished area must have a ceiling of at least 7 ft, except under beams, ducts and other obstructions, where 6 ft 4 in is allowed. Stairs have no height requirement. In a room with a sloped ceiling, at least half of the room's finished area must be 7 ft or higher, and no part under 5 ft is ever counted.
- Does a finished basement count under ANSI Z765?
- It counts as finished area, but not as above-grade area. Under ANSI Z765-2021, a level that is wholly or partly below grade is a below-grade level, so a finished basement (including a walkout) is reported as below-grade finished square footage, on its own line. Any statement of finished area must show the above-grade and below-grade figures separately.
- Do you measure from the inside or outside of the walls under ANSI Z765?
- From the outside. Each level of a detached house is measured at floor level to the exterior finished surface of the outside walls. For attached houses you measure to the exterior finished surface or, where appropriate, to the centerline of the wall shared with the next house. Where finished area meets a garage, you measure to the gypsum surface on the garage side, so the shared wall counts.
- Where can I get a copy of ANSI Z765-2021?
- The standard is sold by its publisher, Home Innovation Research Labs, through its online store at homeinnovation.com. The electronic copy of ANSI Z765-2021 is $25 and runs 16 pages. The earlier 2003 text and the publisher's 2020 public draft of the 2021 edition can be found online for free; the publisher says the 2021 revision did not fundamentally change the standard.