Paint calculator
How many litres of paint for a room, and which packs to buy. Enter the room size and the number of doors and windows.
7.78 litres — buy 2 × 4 L
389 sq ft to paint (389 sq ft of walls), 2 coats, at 100 sq ft per litre per coat.
How it is calculated
- Wall area = 2 × (length + width) × height.
- Minus openings: 21 sq ft per door (7 × 3 ft) and 15 sq ft per window (5 × 3 ft). Add length × width if you are painting the ceiling.
- Litres = area × coats ÷ coverage per litre per coat.
- Packs: largest first; a leftover of 2–3 litres is one 4 L tin, which usually costs less than several 1 L tins.
What coverage should I use?
Use the figure printed on your paint's pack or data sheet — it varies by product and by surface. 100 sq ft per litre per coat is a cautious default for interior emulsion on a smooth, primed wall. Rough, porous or unprimed walls take more paint; a primer coat and putty on new plaster reduce how much emulsion you need.
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