Gross Living Area (GLA) Calculator
Gross living area is not just "add up every room". Classify each space and this calculator applies the ANSI Z765 rules for you, keeping the finished basement out of the headline figure and taking the stairwell void off the floor above.
What counts, and what does not
| Space | Treatment | Rule |
|---|---|---|
| Finished, above grade | Counts toward GLA | Heated and finished living space with no part of the floor below ground level. |
| Open to the floor below | Subtracted from GLA | Stairwell openings and two-storey voids — floor area that is not there. |
| Finished, below grade | Reported separately | Finished basement space. Reported separately from GLA, never added to it. |
| Unfinished space | Not counted | Unheated or unfinished areas such as an unfinished attic or basement. |
| Garage | Not counted | Attached or detached garage space. Excluded from GLA under every standard. |
| Porch, deck or patio | Not counted | Open or screened exterior space. Excluded from GLA even when covered. |
This tool applies the standard's arithmetic to the areas you classify. It is not an appraisal, and it cannot judge whether a space is genuinely finished, heated and tall enough to qualify — ANSI Z765 requires a ceiling height of at least 7 ft over most of the floor area.
What gross living area actually measures
Gross living area is the finished, heated, above-grade floor area of a home, measured to the exterior walls. It is the square footage an appraiser reports and a listing quotes, and it is deliberately narrower than a plain room-by-room total. The point of the definition is comparability: two houses quoted at 2,000 square feet of GLA are offering the same kind of space, whereas two houses quoted at 2,000 square feet of "total area" might not be.
The rules that catch people out
A finished basement is not GLA, however well finished it is. Under ANSI Z765, any level below grade on any side is reported as below-grade finished area on its own line. It still adds value and still belongs on the listing — it simply is not counted in the headline figure, because a buyer needs to know which square feet are above ground.
Stairwells are counted once per floor, and the opening is deducted. The staircase area counts on each floor it serves, but the hole it passes through is subtracted from the floor above. The same applies to a two-storey foyer or an open landing: you cannot count the same vertical space twice.
Ceiling height decides what qualifies. The standard wants at least 7 ft over most of the floor area, dropping to 6 ft 4 in under beams and ducts. Where a ceiling slopes, at least half the floor must reach 7 ft, and only floor with 5 ft of headroom counts at all — which is what limits how much of a converted attic can be included.
For a straightforward materials total with none of these restrictions, use the multi-room calculator instead. The full method behind both, and what this site treats as an estimate rather than sourced data, is set out on the methodology page.
For a plain-language rundown of which spaces count — basements, garages, bathrooms and attics — see what counts as square footage, or the guide to calculating a whole house's square footage.
Frequently asked questions
What is gross living area (GLA)?
Gross living area is the finished, heated, above-grade floor area of a home, measured to the exterior walls. It is the figure appraisers report and listings quote. Under the ANSI Z765 standard it excludes garages, unfinished space and any area below grade, however nicely finished — a finished basement is reported as a separate figure rather than folded into GLA.
Does a finished basement count toward square footage?
Not toward GLA. Under ANSI Z765, any level that is below grade on any side is reported separately as below-grade finished area, no matter how well finished it is. It still adds value and it still belongs on the listing — it is just quoted as its own line, because a buyer comparing two homes needs to know which square feet are above ground.
Do stairs count in gross living area?
Yes, the staircase area counts on each floor it serves, but the opening it passes through is subtracted from the floor above — you cannot count the same vertical space twice. The same applies to a two-storey foyer or an open landing: the void is deducted from the upper floor's area.
What ceiling height does a room need to count?
ANSI Z765 requires at least 7 feet of ceiling height over most of the floor area, dropping to 6 feet 4 inches under beams and ducts. Where a ceiling slopes, at least half the floor area must meet the 7-foot rule, and only the part of the floor with at least 5 feet of headroom can be counted at all — which is what limits how much of a converted attic qualifies.
Is this calculator a substitute for an appraisal?
No. It applies the standard's arithmetic to the areas you classify, which removes the error-prone part of the job, but it cannot judge whether a space is genuinely finished, heated or tall enough to qualify — and those judgements are what an appraiser is paid for. Use it to prepare and sanity-check a figure, not to replace a measurement of record.