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
Measure closets, hallways, and other finished areas separately
Include finished basements only if they are counted in your local standards
Exclude garages, unfinished attics, porches, and unfinished basements unless required
Break irregular spaces into smaller rectangles or triangles and calculate each section
Sum all measured areas to get the total square footage
Verify measurements with a second pass for accuracy