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How is floor space measured?

Floor space is measured by multiplying length by width for each rectangular section and summing the results, but the inclusion rules matter as much as the arithmetic. For a whole home, the US standard is ANSI Z765: measure to the exterior face of the walls, count only finished, heated, above-grade space, and exclude garages, unfinished basements, and open two-story volumes on the upper floor. This produces gross living area (GLA), the figure appraisers and lenders use.

For a single room, measure wall to wall inside the space, which is what flooring and paint estimates need. Commercial properties use different standards again (BOMA), measuring rentable versus usable square footage.

The physical measurement is done with a laser distance meter or tape; the same numbers can also be pulled from a scaled floor plan without visiting the property. That second path is often faster: upload the plan to MeasureFloorPlan, calibrate the scale against one known dimension, and trace either the exterior perimeter for GLA-style totals or individual rooms for interior areas. Either way, the standard you apply determines what counts, so match the method to the purpose.