Guides · Floor Plan Measurement
The same home can have three different square footage numbers depending on who measured it and what they included. Understanding why GLA and total square footage differ is essential for interpreting appraisals, comparing listings, and avoiding surprises at closing.
GLA (Gross Living Area) = above-grade, finished, heated/cooled space measured from exterior walls. It excludes basements of any finish level, garages, carports, unheated porches, and any below-grade space. This is the number on the Fannie Mae/Freddie Mac appraisal form and the standard used for mortgage lending.
"Total square footage" has no single standard definition. It varies by source: County assessor records often include finished basement and sometimes garage. Definition varies by county. MLS listings are agent-entered: some include basement, some don't. No enforcement of a single standard. Zillow pulls from county records or MLS, inheriting whatever errors and inclusions those sources use.
A home with 1,800 sq ft of above-grade GLA and a 900 sq ft finished basement might appear as: Appraisal GLA: 1,800 sq ft (above-grade only). County assessor: 2,700 sq ft (includes finished basement). MLS listing: 2,700 sq ft (if agent included basement). Zillow: 2,700 sq ft (from county records). The appraiser isn't wrong: they're measuring something different than the county.
Mortgage appraisals: GLA required. The appraiser uses above-grade GLA for size adjustments; below-grade finished area gets a separate lower-rate adjustment. Listing square footage: Best practice is to list above-grade GLA and below-grade finished area separately. Many MLS systems now have distinct fields. Lease pricing: Total finished area (including basement) is typically more relevant. Renovation planning: Total finished area for calculating materials, heating load, etc.
Upload the floor plan for each level separately. Draw separate polygons for: above-grade floor 1, above-grade floor 2, finished basement, garage. Label each. Sum only above-grade finished polygons for GLA. Add the basement polygon for total finished area. This gives you both numbers from one consistent measurement source.
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Start Measuring →What's the difference between GLA and total square footage?
GLA (Gross Living Area) is the appraisal standard: above-grade, finished, heated and cooled space measured from the exterior under ANSI Z765. Total square footage is a looser figure that may include basements, garages, and unheated spaces. They can differ by hundreds of square feet on the same home.
Why does Zillow show a different number than my appraisal?
Zillow's number usually mirrors the assessor record or the original MLS listing, which may include finished basement area or use the assessor's own (interior) measurement methodology. The appraisal uses ANSI Z765 GLA. Both are technically correct under their own definitions.
Which number should I list a home with?
Use ANSI Z765 GLA for the appraisal-standard figure, then note any below-grade finished area separately. Combining them into a single "total square footage" without disclosure is what causes the most appraisal-vs-listing disputes.
Does a finished basement count as GLA?
No. ANSI Z765 excludes all below-grade space from GLA regardless of finish quality. Finished basements are reported separately as Below-Grade Finished Area, which is valued differently than above-grade GLA.
Why does this distinction matter for buyers?
Price-per-square-foot comparisons rely on a consistent measurement basis. Comparing a home listed by total square footage against comps listed by GLA produces a misleading per-square-foot value. Always confirm which figure is being used.