Paint Calculator — How Much Paint Do I Need?

A typical 4m × 3.5m living room with a 2.4 metre ceiling needs around 5.5 to 6 litres of emulsion for two coats on the walls — one 5 litre tin plus a 2.5 litre tin with some left over. Add roughly 2.5 litres for the ceiling. A small double bedroom needs about 4.5 litres for walls; a large kitchen-diner can take 9 or more. The calculator does the exact sums from your room's measurements, minus doors and windows.

Manufacturers quote 14 to 16 square metres per litre. On real walls, plan for 12. The printed figure assumes smooth, sealed, previously painted surfaces in ideal conditions. London homes mostly have older plaster with some texture and patching, which drinks more paint. Going from a dark colour to a light one, or painting fresh plaster, uses more still. We estimate at 12m² per litre on every decorating job we price, and we round up — running out of paint mid-wall leaves a visible line where you stopped.

A mist coat is the first coat on bare plaster: standard emulsion watered down 30 to 40%. Fresh plaster is porous and sucks the moisture out of full-strength paint before it can bond, so undiluted paint on new plaster dries on the surface and peels off in sheets, sometimes months later. If your walls have just been skimmed — after a renovation, damp-proofing works, or a media wall build — budget one extra coat's worth of paint and water the first one down. Vinyl and 'durable' emulsions are the worst offenders for peeling off fresh plaster.

Yes to both. Ceilings take a flat matt emulsion — any sheen highlights every roller line and plaster imperfection when light rakes across it. Woodwork — doors, frames, skirting, sills — needs satinwood or gloss, which is a different product entirely: tougher, wipeable, and slower drying. Budget roughly three-quarters of a litre per door including the frame, and half a litre per window. If you're changing woodwork colour or painting over old yellowed gloss, it needs a sand and an undercoat first or the new coat won't grip.