How the numbers work
Wall area = 2 × (length + width) × height, minus about 1.7 m² per standard door (2040 × 820 mm) and 1.5 m² per typical window. Ceiling area = length × width.
Litres = area × coats ÷ coverage, plus 10% for touch-ups and absorbent surfaces. We use 14 m² per litre by default, a slightly conservative figure for interior acrylic; many tins quote 14–16 m². Textured, porous or dark surfaces use more.
Tins: we suggest the combination of 10 L, 4 L and 1 L tins that covers what you need with the least left over.
Don’t forget
- Trims and doors usually use a separate enamel or semi-gloss, about 1 L per door for two coats.
- Patch holes and cracks first (see how to patch plasterboard), then spot-prime the patches.
- Bathrooms and laundries need a paint made for wet areas; ceilings often use a flat ceiling white.
- Painting is DIY-legal everywhere, but homes built before 1970 may have lead paint. Don’t sand or scrape old layers until you’ve checked.
Questions
How much paint do I need for a room?
Work out the wall area (perimeter × height), subtract doors and windows, multiply by the number of coats, and divide by the paint’s coverage (often around 14–16 m² per litre per coat for interior acrylic, check the tin). A typical 4 × 3.5 m bedroom with 2.4 m ceilings, one door and one window, needs roughly 5 litres for two coats on the walls, plus about 2 litres for the ceiling.
How many coats of paint do I need?
Two coats is standard for walls. You may need a primer or sealer first on new plasterboard, patched areas, bare timber, or when changing from a dark colour to a light one.
How much does a 10 litre tin of paint cover?
At about 14 m² per litre, a 10 L tin covers roughly 140 m² for one coat, or 70 m² for two coats. Coverage varies with the product and the surface.
Should I buy extra paint?
Yes, about 10% for touch-ups and absorbent surfaces. Keep leftover paint, labelled with the room, for future repairs.
Estimates only. Check the product label and your measurements before you buy. More free tools: see them all.