🎨 Paint Calculator
Enter your room’s dimensions, the number of coats and your paint’s coverage, and get how much paint to buy — with doors and windows subtracted.
Paint needed
5.42 litres
for 2 coats
Paintable area
29.8 m²
walls 33.6 − openings
Wall area = 2 × (length + width) × height, minus doors/windows, × coats ÷ coverage. Buy whole cans and keep spares. 🔒 In your browser.
How the paint calculator works
The wall area is the room perimeter times the height: 2 × (length + width) × height. The tool subtracts the area of doors and windows, multiplies by the number of coats, and divides by the paint’s coverage rate (how much area one litre or gallon covers) to give the paint needed. Add a little extra for touch-ups and buy whole cans.
Coverage varies by paint and surface — a typical emulsion covers about 10–12 m² per litre (≈ 350–400 sq ft per gallon), but porous or textured walls soak up more. Check the tin and adjust the coverage figure.
Frequently asked questions
How much paint do I need for a room?
Work out the wall area (2 × (length + width) × height), subtract doors and windows, multiply by the number of coats, and divide by the paint’s coverage rate. For a 4 × 3 m room, 2.4 m high, two coats at 11 m²/L, that’s about 6 litres.
How many coats of paint should I apply?
Two coats is standard for good, even coverage. Use three when painting a light colour over a dark one, or on bare or patchy surfaces. One coat rarely looks even.
What is paint coverage?
The area one unit of paint covers — commonly 10–12 m² per litre or 350–400 sq ft per gallon for emulsion. Rough, porous or previously unpainted surfaces cover less, so use the lower figure.
Should I subtract doors and windows?
For a rough estimate you can ignore small openings, but subtracting them (a standard door is about 1.8–2 m²) avoids over-buying on rooms with lots of glazing.
How much extra paint should I buy?
Round up to whole cans and keep a little spare for touch-ups. Buying slightly over from the same batch avoids colour mismatches later.