To calculate paint needed: measure total wall area (length x height for each wall), subtract doors and windows, then divide by paint coverage. Standard paint covers 10-12 sq metres per litre. For a 4m x 4m room (4 walls, 2.5m high): 40 sq metres / 10 = 4 litres for one coat. Add 10% for waste. Two coats = 8 litres total.
📂 Daily Life
🎨 Paint Calculator
Calculate exactly how much paint you need for any room or surface. Enter room dimensions and get the precise litres needed — no more buying too much or running short!
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✨ Your Result
🦉Owl's Explanation
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Fill in the values above and click Calculate ✨
✅ Trusted Tool
The 365tool.net Paint Calculator uses standard coverage estimates for interior latex/emulsion paint. Actual coverage varies by paint brand, surface texture, and application method. Always check the paint tin's stated coverage and buy slightly extra. No sign-up needed.
🤔 How Does This Work?
The Paint Calculator works in three steps:
Calculate total wall area: 2 x (length + width) x height
Subtract door and window areas (1.5m² per door, 1.2m² per window)
Divide net area by coverage per litre, multiply by coats, add 10% waste
❓ Frequently Asked Questions
How do I calculate paint for a room?▼
Calculate wall area: (2 x room length + 2 x room width) x height. Subtract doors (1.9 x 0.8m = 1.5m² each) and windows (1.2 x 1m = 1.2m² each). Divide by paint coverage (10-12m²/litre). Multiply by number of coats. Add 10% waste. Round up to nearest standard can size.
How much does paint cover per litre?▼
Coverage varies by paint type: Matt/flat emulsion: 10-12m² per litre. Silk/satin: 10-11m². Gloss (for wood/metal): 12-14m². Primer/undercoat: 8-10m². Rough surfaces (textured walls, raw plaster) absorb more paint — reduce coverage estimate by 20-30%. Always check the tin for manufacturer's stated coverage.
Do I need primer?▼
Use primer when: painting over bare plaster, dark to light colour change, previously unpainted surfaces, stained walls, or very porous surfaces. Skip primer when: painting similar colour over existing paint, using paint with primer included, or non-porous surfaces. Primer improves adhesion and can mean fewer topcoat layers.
How many coats do I need?▼
New plaster: 3 coats usually needed (1 mist coat + 2 topcoats). Repainting light over light: 2 coats. Dark to light: 2-3 coats. Light over dark: possibly 3+ coats. Primer + 2 topcoats is the gold standard for most projects. Never skip a coat to save time — coverage will be patchy.
What paint type should I use for different rooms?▼
Bathrooms/kitchens: use moisture-resistant or washable paint (silk finish). Living rooms/bedrooms: matt or silk finish works well. Hallways: tough washable paint (silk) handles scuffs. Ceilings: white ceiling paint (usually flat/matt). Children's rooms: washable paint with low VOC. Exterior: specifically exterior formulated paint.
Calculate wall area: (2 x room length + 2 x room width) x height. Subtract doors (1.9 x 0.8m = 1.5m² each) and windows (1.2 x 1m = 1.2m² each). Divide by paint coverage (10-12m²/litre). Multiply by number of coats. Add 10% waste. Round up to nearest standard can size.
How much does paint cover per litre?▼
Coverage varies by paint type: Matt/flat emulsion: 10-12m² per litre. Silk/satin: 10-11m². Gloss (for wood/metal): 12-14m². Primer/undercoat: 8-10m². Rough surfaces (textured walls, raw plaster) absorb more paint — reduce coverage estimate by 20-30%. Always check the tin for manufacturer's stated coverage.
Do I need primer?▼
Use primer when: painting over bare plaster, dark to light colour change, previously unpainted surfaces, stained walls, or very porous surfaces. Skip primer when: painting similar colour over existing paint, using paint with primer included, or non-porous surfaces. Primer improves adhesion and can mean fewer topcoat layers.
How many coats do I need?▼
New plaster: 3 coats usually needed (1 mist coat + 2 topcoats). Repainting light over light: 2 coats. Dark to light: 2-3 coats. Light over dark: possibly 3+ coats. Primer + 2 topcoats is the gold standard for most projects. Never skip a coat to save time — coverage will be patchy.
What paint type should I use for different rooms?▼
Bathrooms/kitchens: use moisture-resistant or washable paint (silk finish). Living rooms/bedrooms: matt or silk finish works well. Hallways: tough washable paint (silk) handles scuffs. Ceilings: white ceiling paint (usually flat/matt). Children's rooms: washable paint with low VOC. Exterior: specifically exterior formulated paint.