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What measurements do floor plans use?

In the US, floor plans use feet and inches, written as 12'-6" (12 feet 6 inches), with dimensions typically precise to the nearest inch or half inch on residential drawings. Metric countries use millimeters for construction drawings (3650 rather than 3.65 m, avoiding decimal errors) and square meters for areas. Areas on US plans are stated in square feet, with gross living area calculated per ANSI Z765 for appraisal and lending purposes.

Scale notation accompanies the measurements: 1/4" = 1' for US residential plans, 1:50 or 1:100 for metric equivalents. Marketing floor plans often simplify to whole feet (12x14) and may omit dimensions entirely. When reading a plan, confirm the unit system first, since a "10x12" room means very different things in feet versus meters, and check whether stated dimensions are interior room measurements or wall-to-wall structural dimensions, which differ by wall thickness.

If you're working with a plan whose measurements are sparse, rounded, or absent, MeasureFloorPlan recovers them in whichever units you need: calibrate the image against one known dimension and measure everything else directly.