Valuation · 5 min read
How to Calculate Price Per Square Foot
Price per square foot is one of the most commonly cited real estate metrics — and one of the most commonly misunderstood. The formula is simple, but what you put in the denominator changes everything.
The formula
Price per square foot = Sale price ÷ Above-grade GLA
Example: A home sells for $420,000 with 1,800 square feet of above-grade GLA. Price per square foot = $420,000 ÷ 1,800 = $233/sq ft.
That is it. The complexity is in knowing which square footage to use.
Why appraisers use above-grade GLA — not total finished area
Appraisers compare properties using above-grade gross living area (GLA) because it is the most consistent measure across different property types. Below-grade space — including finished basements — is valued separately and at a lower rate per square foot.
Mixing above-grade and below-grade square footage into a single price-per-square-foot calculation makes comparisons misleading. A 2,000 sq ft home with 800 sq ft of finished basement is not equivalent to a 2,000 sq ft all-above-grade home — but they look identical if you only look at total finished area.
For a meaningful comparison, use GLA in the denominator and adjust separately for finished basement square footage.
What to include in GLA
- Include: All finished, heated above-grade living space — main level, upper floors, finished attic areas with adequate ceiling height
- Exclude: Garages, unfinished attic, basement (finished or not), covered porches, decks
- Measured from: Exterior wall dimensions (ANSI Z765), not interior
See: What counts as GLA? for a full breakdown.
How to handle finished basements in the calculation
Finished basement square footage is real value — it just sells at a discount relative to above-grade space. Appraisers handle it by:
- Calculating price per square foot using above-grade GLA only
- Identifying the finished basement area as a separate line item
- Applying a dollar-per-square-foot adjustment for the basement — typically 25 to 60 percent of the above-grade rate, depending on market
Example: If above-grade GLA commands $230/sq ft and the market shows finished basements trading at 40% of that, a 900 sq ft finished basement adds approximately $92/sq ft × 900 = $82,800 in contributory value.
Why Zillow and MLS price-per-square-foot numbers are often wrong
Zillow, Redfin, and most MLS systems calculate price per square foot using whatever square footage the listing agent entered — which may include basement area, may be from county records, or may simply be wrong. These numbers are not standardized.
When comparing homes for a purchase decision or an appraisal, always verify what square footage was used in the denominator. A $180/sq ft listing that includes 1,000 sq ft of finished basement is very different from a $180/sq ft listing that is all above-grade.
Getting an accurate square footage for the calculation
The price-per-square-foot metric is only as reliable as the GLA number you feed into it. For a property you are buying, selling, or appraising:
- Do not rely on county assessor records — they are frequently outdated or use inconsistent methodology
- Do not rely on MLS square footage — agents pull from various sources with no consistency requirement
- Use a floor plan from a scan service (CubiCasa, iGUIDE, Matterport) or a licensed appraiser sketch, measured to ANSI Z765 standards
Get accurate GLA before you calculate
Upload a floor plan and get ANSI-compliant above-grade GLA and basement area separately — so your price-per-square-foot calculation uses the right number.
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