House Square Footage Calculator
Calculate total house square footage for real estate listings, appraisals, or renovation projects. Use the multi-segment tool to handle additions, bump-outs, and L-shaped footprints.
House Area Calculator
What counts as house square footage
The ANSI Z765 standard - used by appraisers and most real estate listings - counts only finished, heated, fully enclosed space measured to the exterior wall surface. This means: above-grade finished rooms count; finished basements count separately (and are usually not added to "main" square footage).
Garages, screened porches, unfinished attics, decks, and patios do NOT count as living square footage. They're reported separately in listings ("attached 2-car garage", "covered porch").
Measuring an existing house
Walk the exterior with a tape measure. For each side, measure the longest exterior dimension at the foundation (or, if measuring to siding, account for cantilevers and bump-outs). Sketch the footprint and label every dimension.
For a two-story house with the same footprint upstairs and down, multiply the footprint by 2. For homes with smaller upper floors (Cape Cod, story-and-a-half), measure each floor separately. For tri-levels, measure each level.
Pro tips
Use ANSI Z765 for accuracy
Real estate listings, appraisals, and tax records should follow ANSI Z765. Free PDFs of the standard are available from NAR and HUD.
Don't trust tax records
County tax records often disagree with reality by 10%+ - especially for older homes, additions, and finished basements. Always re-measure for a real estate listing.
Finished basement is "below-grade"
A finished basement gets reported separately as below-grade square footage in MLS listings. Combining it with main living area can be considered misrepresentation.
Subtract open-to-below
A two-story foyer or vaulted great room cuts a hole in your second-floor square footage. Subtract the open-to-below area from the upper floor.