Quickly calculate the net wall area for paint, plaster, wallpaper or tiling — automatically subtracting standard door and window openings.
Add up the length of all four walls (the perimeter), then use that as the 'Wall Length' along with the ceiling height.
A standard interior door is about 21 sq ft (3ft × 7ft) and an average window is about 15 sq ft — adjust these if yours are a different size.
Yes — net wall area after subtracting openings is exactly what you need for paint, wallpaper, plaster or tile quantity calculations.