Paint Calculator
How much paint a room needs, after doors, windows and coats.
How it works
Wall area is the perimeter times the height, less the openings. A standard door is about 1.8 m² and a typical window 1.4 m².
Coverage is on the tin, usually 10-12 m² per litre, but that figure assumes a smooth sealed surface. Bare plaster, textured render and anything porous drink noticeably more — the first coat on new plaster can take half again.
Buy for the whole job at once. Batch-to-batch colour variation is real and very visible on a wall finished in two sittings.