Wall Area Calculator

The area of the walls in a room is the perimeter multiplied by the ceiling height: twice the sum of the length and width, times the height. That figure covers all four walls at once and is the starting point for painting, papering, cladding or insulating, though most projects then deduct the openings, because you do not paint the glass in a window or the panels of a door. Deductions are worth making but easy to overestimate. A standard interior door is around twenty square feet and a typical window ten to twenty, so a room with three openings loses forty to sixty square feet of wall. That is worth taking off a large wall but makes little difference in a small room, and leaving a little contingency for around frames and reveals is normal when buying paint. Ceilings are added separately, because their area is simply length times width and they are often painted in a different product and colour. Cornices, skirting and picture rails are measured in linear feet rather than square feet, and they are a useful by-product of the same measurements, since the perimeter you already have is exactly the run of skirting the room needs. This calculator gives the gross wall area, deducts a standard allowance for openings, and optionally adds the ceiling, with the room's perimeter for trim. It assumes square corners and standard openings. For irregular rooms, split into rectangles and add, and measure the actual height from floor to ceiling in more than one place, because ceilings are rarely perfectly level.

This calculator returns estimates for planning and general information only. It is not engineering, architectural, structural, electrical or code advice, and it cannot replace a qualified professional who has seen the site. Material quantities depend on the actual dimensions, the product you buy and local building codes, so confirm the figures before ordering materials or starting work, and always follow local regulations.