iGuide Method of Measurement



Interior Area is a per floor calculation, made by measuring to the inside surface of the exterior walls. Prescribed area exclusions can vary from region to region. Examples of exclusions are spaces open to below, garages, cold cellars, crawl spaces, non-enclosed open spaces, such as decks and balconies. The footprint of all interior walls and staircases is typically included in the reported Interior Area. The iGuide PDF floor plans use a distinct color to highlight all included areas. They should be referenced for details on included and excluded areas.

Exterior Area is a per floor calculation, made by measuring to the outside surface of the exterior walls.

Grade is the ground level at the perimeter of the exterior finished surface of a house. A floor is considered to be above grade if its floor level is everywhere above grade.

Total Interior Area (Above Grade) is the sum of all Interior Areas (above grade).

Total Exterior Area (Above Grade) is the sum of all Exterior Areas (above grade).

Total Interior Area Below Grade is the sum of all Interior Areas below grade.

Ceiling Height is the distance between ceiling and floor level for the majority of a floor, excluding vaulted areas.


iGuide Exterior Area Calculation

Exterior Area = [Perimeter Wall Thickness] x [Perimeter Wall Length] + [Interior Area]


  1. Perimeter Wall Thickness is an independent measurement taken from the property, typically, at the main entrance. Considerations are not made for varying wall thickness around the perimeter.
  2. Perimeter Wall Length is the sum of lengths of all exterior wall segments on a particular floor. When used to calculate Total Exterior Area Above Grade based on Total Interior Area Above Grade, it is the sum of perimeter wall lengths of all floors above grade.



All dimensions and floor areas must be considered approximate and are subject to independent verification.