Guides · Floor Plan Measurement

How to Measure Square Footage of an Open Floor Plan

Open floor plans — where kitchen, dining, and living areas combine without interior walls — are among the easiest floor plans to measure. There are no interior walls to work around; you trace the full exterior perimeter of the above-grade finished space and you're done. Here's how to handle every detail.

The basic approach: one polygon, exterior perimeter

For GLA measurement you always trace exterior walls regardless of interior layout. An open plan doesn't change this. Trace the outside face of the exterior walls as one continuous polygon, excluding the garage and any unheated porches. The absence of interior walls actually makes open plans easier to trace than compartmentalized floor plans — fewer corners, more continuous perimeter.

Handling the garage

The most common element to exclude. On most floor plans the garage is clearly delineated — often labeled "Garage" with a distinct wall. Trace the living area perimeter up to the garage wall and around it. If you want the garage area separately, draw a second polygon around the garage after finishing the main polygon.

Handling columns and posts

Open floor plans often use structural columns instead of walls. Columns appear as small squares or circles on the plan. Don't trace around individual columns — trace the outer perimeter of the floor space as if columns weren't there. Each column occupies only a few square inches of floor area and is not excluded from GLA.

Half-walls and partial walls

Some open plans have knee walls or low partitions defining zones without fully enclosing them. These are interior elements — trace the exterior perimeter and ignore internal partitions. They don't affect GLA.

Covered patios and deck connections

Modern homes often connect to large covered patios via sliding glass doors. Outdoor areas are not GLA. Follow the exterior wall of the home — if there's a large sliding door opening to a patio, trace the outside of that wall just like any other wall. The patio is outside your polygon.

Irregular exterior edges

Open plans often have more complex exteriors — bump-outs, bay windows, angled walls. Place a polygon point at every corner of the exterior wall. For bay windows trace around the outer edge of the bay (it's conditioned space). For curved walls approximate with closely-spaced straight segments. The tool handles any number of corners and any shape.