Measure the length of each room in feet
Measure the width of each room in feet
Multiply length by width to get each room’s square footage
Add the square footage of all finished rooms
Include closets, hallways, and other finished interior spaces
Exclude unfinished areas such as garages, attics, basements, and porches unless they are finished and counted in your area standard
For irregular spaces, divide the area into smaller rectangles or triangles, calculate each part, then add them together
For multi-level homes, calculate each floor separately and add the totals
Use the same measurement standard throughout the house
Verify measurements with a tape measure or laser measure