Calculate exactly how much paint you need. Enter room or wall dimensions, number of coats, and get litres required and estimated cost.
Calculate floor, wall, and sloped surface areas from dimensions
Emulsion: 10-14 m²/L per coat on smooth walls. Gloss/eggshell: 12-15 m²/L. Masonry paint: 6-8 m²/L on rough render. Primer: 8-12 m²/L. Always check the tin — coverage varies by manufacturer and surface texture.
Two coats is standard for a colour change. Three coats for dark colours over light, or when painting over strong existing colours. Use a primer/sealer first when covering very dark walls or stains.
New plaster needs a mist coat (diluted emulsion at 70:30 paint:water) before the first full coat. Allow new plaster to dry fully — typically 4-6 weeks for sand/cement plaster, 1-2 weeks for skim coat.
Order 10% extra for touch-ups and wastage. Keep leftover paint sealed and stored upright in a frost-free location for future touch-ups. Write the room name on the tin with a marker.
A = wall_area - openings
V = (A × coats) / coverage_per_litre
V_total = V × 1.10
cost = V_total × price_per_litre
For lead paint removal (pre-1970s properties), specialist encapsulation or removal is required by law. For high-rise exterior painting, use a qualified contractor with appropriate access equipment and insurance.
Wall area = 2×(4+4)×2.4 = 38.4 m². Minus 1 door (1.9) + 1 window (1.5) = 35.0 m². Ceiling = 16 m². Total = 51 m². Two coats at 12 m²/L: 51×2/12 = 8.5L. Buy 2×5L tins.
Trade emulsion: £3-6/L. Designer emulsion: £8-15/L. Gloss: £5-8/L. Masonry: £3-5/L. Buying 5L tins is cheaper per litre than 1L tins. Trade paint is generally better value than retail.
Yes — enter the wall dimensions and use masonry paint coverage (6-8 m²/L on rough render). Add 15% waste for exterior work due to overspray and uneven surfaces. Don't paint in direct sunlight or below 5°C.
Unopened: 2-5 years if stored correctly. Opened: 1-2 years if resealed properly. Water-based paint that has been frozen is unusable. Oil-based paint lasts longer but check for skinning before use.