How much paint
do you actually need?

Measure the perimeter of the room, multiply by the ceiling height, then take away roughly two square metres for each door and one and a half for each window. Divide by the coverage on the tin (usually 12 to 14 square metres per litre for emulsion), multiply by two coats, and add ten percent. A typical 4 by 3.5 metre bedroom with a 2.7 metre ceiling needs about 6 litres of emulsion for the walls.

Coverage figures on tins are measured on smooth sealed boards. Filled patches, bare plaster, textured render and rough harl all absorb far more. Rollers hold paint too. We use conservative figures and add a margin, and we still suggest buying the first coat and measuring what you actually used before ordering the rest.

Two full coats is the honest minimum for a lasting finish on a sound surface in a similar colour. Change from dark to light, paint new plaster or use a strong red or yellow and plan for three. Limewash is different: four or more thin coats built up slowly.

Almost always per litre, but only if you will use it. Leftover paint in an open ten litre tin skins over and goes off within a year or two. Buy what the calculator suggests plus a little for touching up, and decant the spare into a smaller sealed container.

Paint is usually a small share of a professional job. Most of the cost is preparation and skilled time. Our pricing page explains how we build a quote and what a typical room, hall or exterior costs in Fife.