How Much Paint Do I Need?
One of the most common questions from DIY painters is "how many litres do I need?" The answer depends on three things: the total area you're painting, how many coats you need, and the coverage rate of your chosen paint.
Formula: Wall area (m²) ÷ coverage per litre × number of coats = total litres needed.
Most interior paints cover 14–17m² per litre per coat. Exterior paints typically cover 10–14m² per litre because they're thicker and go onto more porous surfaces. Premium paints often achieve full coverage in 1 coat, while economy paints usually need 2–3 coats.
How to Measure Your Wall Area
To calculate your wall area:
- Measure the length of each wall in metres
- Multiply by ceiling height (standard Australian ceiling is 2.4m)
- Add up all wall areas
- Subtract windows (~1.5m² each) and doors (~1.8m² each)
For example, a 4m × 5m bedroom: (4+5+4+5) × 2.4 = 43.2m². Subtract 2 windows (3m²) and 1 door (1.8m²) = 38.4m² of paintable wall area. That's close to our default value.
Interior vs Exterior Paint: What's the Difference?
Interior and exterior paints are formulated differently and are not interchangeable:
| Property | Interior Paint | Exterior Paint |
|---|---|---|
| UV resistance | Low — will fade outdoors | High — UV-stabilised for Australian sun |
| Flexibility | Minimal expansion needed | Flexible — handles temp. expansion |
| Mildew resistance | Low | Contains mildewcides for humidity |
| Scrubability | High — easy to clean | Moderate — needs to be tougher |
| VOCs | Low-odour options widely available | Higher VOCs typically |
| Drying time | 1–2 hrs to touch | 30 min–2 hrs (weather dependent) |
| Coverage per litre | 14–17m² | 10–14m² |
Never use interior paint on exterior surfaces — it will peel and fail within months in Australian conditions. Similarly, exterior paint is overkill for indoor use and has higher VOCs (volatile organic compounds) that can be unpleasant in enclosed spaces.
Australian Paint Brands
Australia has a strong paint manufacturing industry. Here are the major brands you'll find at Bunnings, hardware stores and trade centres:
- Dulux — Market leader. Interior: Wash&Wear, Kitchen & Bathroom. Exterior: Weathershield, Acratex (textured). Premium range: $70–$120/L
- Taubmans — Owned by PPG. Interior: Endure, Easycoat. Exterior: All-Weather, Sunproof. Mid-range: $50–$90/L
- British Paints — Budget-friendly brand. Interior: 4-in-1 Ceiling, 4-in-1 Walls. Exterior: Weatherguard. Economy: $25–$50/L
- Haymes Paint — Australian-owned (Victoria). Premium interior: Expressions, Velvey Touch. Exterior: Super Cover, Cabot's timber stains. $60–$110/L
- Walpamur — Trade-focused brand from Dulux. Interior: Paintshield. Exterior: Trade Weathershield. Trade prices: $40–$70/L
Worked Example 1: 3-Bedroom House Interior
You're painting the interior walls of a standard 3-bedroom Australian home (~200m² of wall area across all rooms).
- Wall area: 200m²
- Paint: Dulux Wash&Wear (premium, interior, ~15m²/L coverage)
- Coats: 2 coats
- Per coat: 200 ÷ 15 = 13.3L
- Total litres: 26.6L → buy 4 × 8L tins (32L) for touch-ups
- Cost at ~$80/4L equivalent: ~$640 for paint only
- Labour (painter at $55/hr, ~3 days): ~$1,320
- Total: ~$1,960 or about $10/m² for labour and materials
Worked Example 2: Exterior Weatherboard Home
Painting the exterior of a weatherboard Queenslander home in Brisbane — about 150m² of wall area.
- Wall area: 150m²
- Paint: Dulux Weathershield (exterior, ~12m²/L)
- Coats: 2 coats
- Per coat: 150 ÷ 12 = 12.5L
- Total litres: 25L → buy 4 × 8L tins or 5 × 4L + 1 × 8L
- Cost at ~$90/4L: ~$550
- Additional: Primer (~$150), caulking, pressure cleaning
- Labour: ~$1,800 (exterior takes longer — weatherboards cut in)
- Total: ~$2,500
Premium vs Economy: Which Should You Choose?
The choice between premium and economy paint comes down to where you're painting and how long you want it to last:
- Premium paint ($60–$120/L): Better coverage (often 1-coat hide), superior washability (scrub 10,000+ times), fade-resistant, 7–10 year lifespan on interior. Worth it for living areas, hallways, kitchens and kids' bedrooms where walls get dirty.
- Economy paint ($25–$45/L): Lower coverage (needs 2–3 coats), less washable (scrub up to 2,000 times), may chalk or fade in 2–4 years. Suitable for ceilings, rental properties, temporary spaces, or colours you know you'll repaint soon.
Pro tip: If you're using a dark colour over a light wall, you may need a tinted primer regardless of the paint quality — primer is cheaper than premium paint and gives better coverage.
Paint Coverage Guide
| Surface | Paint Type | Coverage per Litre | Cost per Litre |
|---|---|---|---|
| Interior walls (smooth) | Interior low-sheen | 14–17m² | $30–$100 |
| Interior ceiling | Ceiling white | 12–15m² | $25–$60 |
| Exterior brick | Exterior masonry | 8–10m² | $50–$110 |
| Exterior weatherboard | Exterior gloss | 10–12m² | $50–$100 |
| Fences / decking | Exterior timber | 6–10m² | $40–$80 |
5 FAQs About Painting in Australia
For a standard 4m × 5m bedroom (43m² wall area): ~3L per coat or ~6L for 2 coats. Buy a 4L tin for walls and a 4L tin for the ceiling. Always buy more than you think you need — leftover paint is useful for touch-ups and you can't colour-match perfectly if you run out mid-project.
Interior paint is designed for easy cleaning, low odour, and scuff resistance. It lacks UV stabilisers — using it outside causes fading and peeling within months. Exterior paint has UV protection, flexible resins for temperature expansion, and mildewcides for Australian humidity. Always use paint rated for your specific application — interior walls, exterior walls, ceilings, and trims all have different requirements.
Interior smooth walls: 14–17m² per litre. Exterior walls: 10–14m² per litre. Rough surfaces (brick, render): 8–12m² per litre. Ceilings: 12–15m² per litre. These are manufacturer-rated coverages — actual coverage depends on application method (roller vs spray), surface porosity, and how thickly you apply the paint.
Water-based acrylic: touch dry 1–2 hours, recoat 2–4 hours. Oil-based enamel: touch dry 6–8 hours, recoat 16–24 hours. In Australian summer heat, water-based paint can be touch dry in 30 minutes but still needs 4 hours between coats. Don't paint in direct sunlight or when rain is forecast — both will ruin the finish. Ideal painting conditions: 15–30°C, low humidity.
Premium paint ($60–$120/L) offers 1-coat coverage, superior washability, and lasts 7–10 years. Economy paint ($25–$45/L) needs 2–3 coats and lasts 2–4 years. For high-traffic areas (hallways, kitchens, kids' rooms), premium is a better long-term investment. For ceilings, rental properties, or rooms you'll repaint soon, economy is fine. The labour cost is the same either way — don't cheap out on materials if you're paying a painter by the hour.