Paint calculator
Litres of paint, primer and putty for a room or the whole house — with real coverage rates per system (interior/exterior emulsion, distemper, enamel) and the answer split into the tin sizes shops sell.
Over wall putty and primer — bare plaster drinks far more paint.
Measuring the paintable area
Walls both sides, ceilings, minus openings — it adds up fast and is easy to under-measure. Generate a floor plan and the materials card computes the paintable area from the validated plan’s walls and ceilings and pre-fills it here.
Common questions
How much paint for a 12×12 room?
A 12 × 12 ft room with a 10 ft ceiling has roughly 40 m² of paintable wall after a door and window, plus 13 m² of ceiling. Two coats of interior emulsion at 12.5 m²/L per coat come to about 8.5 litres — a 10 L tin with a little left for touch-ups.
How many litres of paint per square metre?
Interior emulsion covers about 12–13 m² per litre per coat over a puttied, primed surface; exterior emulsion about 8–9 because the surface is rougher and the film thicker. Two coats are standard, so divide your area by ~6 (interior) or ~4 (exterior) for total litres.
Do I need putty and primer?
On new plaster, yes — two coats of putty (about 1.2 m² per kg) level the surface and one coat of primer (about 10 m²/L) seals it. Skipping them makes the plaster drink paint, and the finish shows every trowel mark. On repaint jobs in good condition, primer alone is often enough.
What tin sizes should I buy?
Emulsion is sold in 1, 4, 10 and 20 litre packs, and the per-litre price falls sharply with size. The calculator splits your total greedily from 20 L down — the same way a paint shop will quote it.