Guides · Floor Plan Measurement

How to Measure a Condo Floor Plan for Square Footage

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.

Why condo measurement is different

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.

Common condo measurement conventions

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.

How to trace a condo floor plan

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.

What to include and exclude

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.

Reconciling with condo association records

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.