Paint Calculator
Estimate how much paint you need for walls and ceilings. Enter room dimensions, number of coats and coverage rate to get the total litres and recommended can sizes.
Tip: set Height to 0 to enter a total paintable area in the Length field.
Your result will appear here.
Paint Calculator online
Estimate how much paint you need for walls and ceilings from room dimensions, coats and coverage rate. The tool handles both room-mode (with door/window deductions) and direct area input. The result includes total litres and a practical can-size breakdown so you can buy exactly what you need.
How it works
The calculation is straightforward: Litres = Total Area × Coats ÷ Coverage Rate × (1 + Waste / 100). In Room mode the wall area is 2 × (Length + Width) × Height, minus door/window area. To include a ceiling, add its area (Length × Width) to the total. In Area mode, set Height to 0 and enter the total paintable area in the Length field. The default coverage rate is 10 m²/L for typical interior emulsion; the default waste is 10% for brushing/rolling losses and uneven surfaces.
Worked example
A bedroom 4 m long, 3 m wide, 2.5 m high, two coats, default 10 m²/L coverage, 10 % waste. Wall area = 2 × (4 + 3) × 2.5 = 35 m²; minus one door (2 m²) and one window (1.5 m²) = 31.5 m². Ceiling = 4 × 3 = 12 m². Total = 43.5 m². Litres = 43.5 × 2 ÷ 10 × 1.10 = 9.57 L. Recommended purchase: 10 L + 1 L cans.
Coverage rate reference
- Interior emulsion (matte/silk): 10–12 m²/L
- Ceiling paint (flat): 10–11 m²/L
- Primer / undercoat: 8–10 m²/L
- Wood/metal enamel: 12–14 m²/L
Practical tips
- Always round up to the next whole can — you cannot buy half a litre.
- Dark colours covering light walls may need an extra coat; increase Coats by 1 in that case.
- Subtract doors, windows and large openings from the wall area; a standard door is ~2 m², a window ~1.5 m².
- This is a planning estimate. Actual coverage depends on surface porosity, application method and brand — confirm with the manufacturer's data sheet before buying.
Privacy and browser processing
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Frequently asked questions
What coverage rate should I use for standard wall emulsion?
Use 10 m²/L as a safe default for typical interior matt or silk emulsion. Check the tin — manufacturers often state 10–12 m²/L. If the surface is very porous (new plaster), drop it to 8–9 m²/L.
Do I need to include the ceiling?
Only if you are painting it. Add the ceiling area (Length × Width) to the total, or use area mode.
How do I account for doors and windows?
Enter the number of standard doors (~2 m² each) and windows (~1.5 m² each). The tool subtracts their total area from the wall area automatically.
What if I am painting a dark colour over a light one?
Increase Coats by 1. Two coats of a dark colour over white often leave patchiness; three coats gives an even finish.
Is this tool free?
Yes. It is free and does not require an account.
Does DailyWebKit upload my input?
No. It runs locally in your browser and your input is never uploaded.