Calculations for the square footage of a home are taken from
the outside dimensions of the structure (so exterior and interior wall
thickness is included). If your home exterior is easily accessible, you can
do it yourself with a 100-foot tape measure.
Any space that has walls (knee walls 5 ft or higher), flooring, ceiling
(7 feet or higher for at least half of the room’s floor area) and permanent
heat would count as finished square footage. Spaces not permitted can be
counted but should be disclosed as “non-permitted”. This can vary by state.
For multi-level or transitional homes, calculating square footage should be
done by a professional for accuracy as measuring from the outside is not