Guides · Floor Plan Measurement
Measuring a condo requires a choice that doesn't exist for single-family homes: should you measure from exterior walls (ANSI Z765 GLA) or from interior walls (wall-to-wall)? The answer depends on your purpose, local convention, and the condo association's practices.
Single-family homes have clear exterior walls on all sides. Condos share walls with adjacent units. The "exterior" of your unit includes shared party walls you don't exclusively own. Many condo regimes define unit size using interior dimensions (inside faces of perimeter walls) rather than exterior dimensions. As a result, condo square footage conventions vary significantly by market and condo association.
Interior net area (most common for residential): Measured from the inside face of the unit's perimeter walls. What buyers think of as "how much space do I have." Exterior gross area: Measured from the outside of shared walls (or centerline for party walls). Larger than interior net. More common in appraisal work. BOMA standards: Some high-rise condos use BOMA Residential standards. Less common for typical residential resale.
For interior net area: Trace the inside face of all perimeter walls. Click along the interior wall line around the full unit perimeter. For exterior-equivalent measurement: Trace the outside face of perimeter walls, using the centerline for shared party walls. This produces a larger number consistent with ANSI Z765 exterior methodology.
Include: All finished, heated living space exclusive to your unit: bedrooms, living areas, kitchen, bathrooms, hallways, closets within the unit perimeter. Exclude: Balconies and terraces (report separately as they're typically not GLA), storage units outside the main unit, common hallways, parking spaces.
Many condo associations publish official unit sizes. If your measurement differs, check which method each uses. A 2–4% difference might be entirely due to interior vs exterior convention. A 10%+ difference warrants a closer review of what exactly is being included in each number.
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Start Measuring →How is a condo measured differently from a single-family home?
Condos typically use interior (wall-to-wall) measurement rather than exterior. The reason: condo owners only own the interior of their unit, not the exterior walls (which are common elements). This is the BOMA convention for residential condos.
Should I use GLA or interior measurement for a condo?
For an appraisal, use whatever the local market and lender require. Most condo markets standardized on interior measurement decades ago. For ANSI Z765 GLA (still required by Fannie/Freddie), use exterior measurement to the unit's outermost demising walls.
What's the difference between a condo's interior and exterior square footage?
Interior measurement is typically 5 to 10 percent smaller than exterior measurement, depending on the thickness of demising walls and exterior walls. The two figures should be clearly distinguished in any listing or appraisal.
How do I measure a condo from a floor plan?
Upload the floor plan, trace the unit's perimeter (interior wall surface for BOMA, exterior wall surface for ANSI), and set scale from any labeled wall dimension. The tool returns area instantly.
Are balconies and storage included in condo square footage?
Generally no, unless the listing explicitly mentions them. Balconies, terraces, and exterior storage are usually reported separately or excluded from the headline square footage figure.