‘Square footage’ means something specific in real estate: finished, above-grade living area measured a particular way. Since 2022, Fannie Mae has required appraisers to use the ANSI Z765 method, so knowing its rules helps you understand listings, appraisals and tax records. This guide explains what counts, what doesn’t, and how it’s measured.
What’s in this guide
The standard: ANSI Z765
The ANSI Z765 standard, Square Footage – Method for Calculating, defines gross living area (GLA) for single-family homes. It is measured from the exterior of the walls and includes only finished, above-grade space. Fannie Mae has required its use for appraisals since April 2022.
Those three words define GLA. Miss any one and the number is wrong for real-estate purposes.
What counts and what doesn't
| Counts in GLA | Excluded from GLA |
|---|---|
| Finished bedrooms & living areas | Garage (attached or detached) |
| Finished hallways & closets | Unfinished attic or basement |
| Finished above-grade additions | Finished basement (reported separately) |
| Enclosed, heated finished space | Open porches, decks, patios |
| Stair openings (counted once, per level) | Spaces open to the floor below |
How square footage is measured
- Measure each level from the exterior walls, to the nearest inch, then compute length × width.
- Break the footprint into rectangles for L- and T-shaped homes and add them.
- Exclude non-qualifying areas: garage, unfinished space, and anything below grade.
- Apply the ceiling-height rule to attics and rooms with sloped ceilings.
- Add the finished above-grade levels for total GLA; list basement area separately.
Worked example: a two-story home
| Area | Size | In GLA? |
|---|---|---|
| First floor (finished) | 1,000 sq ft | Yes — 1,000 |
| Second floor (finished) | 900 sq ft | Yes — 900 |
| Attached garage | 400 sq ft | No |
| Finished basement | 800 sq ft | Reported separately |
| Gross Living Area | — | 1,900 sq ft |
Ceiling height rules
| Situation | Rule |
|---|---|
| Standard finished room | Needs ≥ 7 ft ceiling to count |
| Sloped / attic ceiling | ≥ 50% of the floor must be 7 ft or higher |
| Under a slope | No area below 5 ft counts |
| Beams / ducts | Localized low spots are generally ignored |
Common mistakes
Even a beautiful finished basement is reported separately, not added to gross living area.
GLA is measured from the exterior walls; interior measurements understate it.
A garage is never finished living area, no matter how nicely it's kept.
Key takeaways
- Square footage = finished, above-grade GLA, measured from the exterior.
- The ANSI Z765 standard governs it and is required by Fannie Mae.
- Garages, unfinished space and basements are excluded from GLA.
- Finished areas need ≥ 7 ft ceilings (50% rule under slopes).
Related calculators & guides
Frequently asked questions
- How is house square footage calculated?
- Under the ANSI Z765 standard, measure the finished, above-grade area from the exterior walls and add each level together. Garages, unfinished areas and below-grade space (even finished basements) are excluded from gross living area (GLA) and reported separately.
- Does a finished basement count as square footage?
- Not in gross living area. Below-grade space is reported separately from GLA even when fully finished, because appraisers and the ANSI standard treat above- and below-grade area differently.
- Is the garage included in square footage?
- No. Garages, whether attached or detached, are excluded from finished living area. So are open porches, unfinished attics and spaces open to the floor below.
- What ceiling height counts toward square footage?
- A finished area generally needs at least 7 ft of ceiling height to count. Under a sloped ceiling, at least half the floor must be 7 ft or higher, and no area under 5 ft is counted.