Exterior Paint Calculator Australia — Walls, Fascia, Eaves & Trim
Exterior walls
Perimeter × average wall height. Deduct large windows and doors if significant.
Fascia & eaves (optional)
Eave depth × perimeter. Typical: 450–600 mm eave × house perimeter.
Fascia is typically 190 mm wide — calculator uses 0.19 m² per LM.
Doors & trim (optional)
Each door = approx. 3.5 m² (both sides + frame, 2 coats).
Architraves, reveals, sill mouldings — approx. 0.1 m² per LM.
Exterior paint required
Wall paint
Fascia, eaves & trim paint
Total
This exterior paint calculator estimates litres of paint for all surfaces of an Australian home exterior — walls, eaves, fascia boards, doors, and trim. Coverage rates are set for common Australian exterior surfaces: rendered brick 9 m²/L, weatherboard 12 m²/L, fibre cement (Scyon/Hardiflex) 10 m²/L, and bare or raw substrates lower. Exterior paints typically have a lower spread rate than interior paints due to texture, porosity, and thicker film builds required for UV and weather resistance. The calculator is brand-neutral — always verify the spread rate on your product's data sheet before ordering.
Frequently Asked Questions
What is the best exterior paint for Australian conditions?
Australian conditions — UV intensity, heat cycling, and coastal salt in coastal areas — demand exterior paints with high UV resistance, good elasticity, and mould resistance. Acrylic latex exterior paints are the industry standard, with premium options offering 10–15 year warranties. In bushfire-prone areas, look for products with BAL (Bushfire Attack Level) ratings. For rendered masonry, a breathable acrylic formula prevents moisture trapping under the paint film.
How do I measure exterior wall area?
Measure the external perimeter of the building and multiply by the average wall height from the finished ground level to the eave. For a simple rectangular house: add the four wall lengths and multiply by height. Deduct the area of very large windows, garage doors, and other large openings. Small windows and doors generally don't need deducting when you have a 10% wastage buffer included.
Do I need to prime before painting an exterior?
Yes, for bare or porous surfaces. Bare timber, new fibre cement, unpainted render, and previously unpainted brick all require a primer or sealer coat before topcoating. Priming improves adhesion, reduces paint consumption, and prevents efflorescence (salt deposits) on masonry. Previously painted surfaces in good condition can usually be recoated without primer, after thorough cleaning and sanding of flaking areas.
How often should an Australian home exterior be repainted?
In most Australian climates, a quality exterior repaint lasts 7–12 years depending on surface type, paint quality, and sun exposure. North-facing walls and west-facing walls receive the highest UV load and typically show fading earlier. Coastal homes in salt-air environments should be repainted every 5–8 years. Dark colours fade more visibly than light colours and may need recoating sooner.
What is the coverage difference between interior and exterior paint?
Exterior paints are formulated with a thicker film build for durability and weather resistance, which reduces their spread rate compared to interior paints. A typical exterior acrylic on rendered masonry covers 9–12 m²/L, versus 12–16 m²/L for interior flat paint on smooth plasterboard. Rough or porous exterior surfaces can drop to 6–8 m²/L. Always use the spread rate from the product data sheet, not the label.
How to use this calculator
- Enter wall area — measure the total exterior wall area in m². A simple method: measure the perimeter of the house, multiply by wall height (typically 2.7–3.0 m), then subtract approximate openings (each door ≈ 2 m², each window ≈ 1.5 m²).
- Select surface type — this significantly affects coverage rate. Weatherboard (primed or painted) covers approximately 12 m²/L; rendered masonry 9 m²/L; fibre cement 10 m²/L; bare or heavily porous surfaces 6–7 m²/L.
- Enter number of coats — previously painted surfaces in good condition typically need 2 coats; bare or heavily weathered surfaces may need a primer plus 2 top coats (enter 3).
- Add eave, fascia and trim areas — these surfaces often use a different paint sheen or colour and are calculated separately. Fascia and trim are typically measured in linear metres.
- Read the result — litres required by surface type and a recommended tin purchase quantity.
Worked example: Single-storey weatherboard home, 180 m² total wall area, 2 coats. Coverage at 12 m²/L × 2 coats = 30 L. Add fascia 40 lm at 0.5 L/lm = 20 L. Total ≈ 50 L. Buy two 10 L tins with a small buffer, or ask for a 15 L trade pack from your paint supplier.
Understanding your results
The calculator returns total litres by surface type and a recommended tin purchase quantity. Coverage rates (weatherboard 12 m²/L, render 9 m²/L, fibre cement 10 m²/L, bare 6–7 m²/L) are based on typical Australian exterior paint products applied by brush and roller — spray application can improve coverage by 10–15% on smooth surfaces.
These coverage figures assume a sound, clean, prepared surface. Heavily weathered, chalky, or bare surfaces absorb significantly more paint and will use closer to the lower end of the coverage range. Always apply a suitable primer or sealer on bare or very porous surfaces before top-coating — trying to cover them with two coats of top coat alone leads to poor adhesion and early failure.
Exterior paint is typically sold in 4 L, 10 L, and 15 L sizes at trade suppliers (Dulux Trade, Taubmans, Haymes, Solver). Buying in larger tin sizes reduces cost per litre — compare unit pricing before purchasing.
Common mistakes: Painting over dirty, chalky or wet surfaces; applying too thickly in one coat rather than two thin coats; not stirring paint thoroughly before use; and underestimating coverage on rough-textured render or unpainted surfaces.
Exterior painting in Australia — surface prep and product selection
Exterior painting in Australia is significantly affected by climate. UV radiation, heat, humidity, and temperature cycling all degrade paint film far faster than in cooler climates — which is why Australian exterior paints are specifically formulated for harsh local conditions. Correct surface preparation and product selection is the difference between a paint job that lasts 5 years and one that lasts 12+.
Surface preparation — the most important step
Regardless of paint quality, a poorly prepared surface will fail. For previously painted surfaces: wash with sugar soap to remove dirt, grease and chalky residue; sand back any flaking or cracking paint to a firm edge; spot-prime bare areas with an appropriate primer. For severely chalky surfaces, apply a stabilising primer before top-coating. For bare timber (new weatherboard): apply a full coat of oil-based or water-based primer before applying top coats.
Choosing the right sheen for exterior
For rendered walls and fibre cement: low sheen or flat is most common and hides surface imperfections. For fascia, eaves and trim: semi-gloss or gloss provides a durable, moisture-resistant finish that's easy to clean. For weatherboard walls: low sheen is standard, though gloss was historically used and is still preferred by some for its moisture resistance on timber.
Paint selection for Australian conditions
In tropical North Queensland and the NT, choose a paint with high mould resistance. In coastal areas, choose a product with salt resistance. In alpine or frost-prone areas, ensure the paint has a low-temperature application rating — most exterior paints should not be applied below 10°C. Dulux Weathershield, Taubmans Endure Exterior, and Haymes Equiseal are specifically formulated for Australian exterior conditions.
When to paint
Do not apply paint in rain, direct hot sun (above 35°C), high winds, or when rain is expected within 4 hours. Early morning in summer is ideal — surfaces are cool and drying conditions are good. Painting in direct sun heats the surface above the air temperature, causing paint to dry too fast on the surface and preventing proper film formation and adhesion.
Licensing requirements
In Queensland, NSW, Victoria and WA, painting contractors working on residential properties above a certain contract value must hold a licence from the relevant building authority (QBCC, Fair Trading NSW, VBA, BSCL respectively). Always ask for a contractor's licence number and verify it before signing a contract.
Australian standards and references
- AS/NZS 2311:2017 — Guide to the painting of buildings (paint application, surface preparation, and coating selection)
- AS/NZS 2310:2002 — Glossary of paint and painting terms
- Master Painters Australia (MPA) — Technical guidance, specification documents and contractor standards for professional painting
- NATSPEC — National specification system including painting specification clauses for commercial and residential projects
- Dulux, Taubmans, Haymes, Solver Technical Data Sheets (TDS) — Manufacturer-specific coverage rates, application conditions and surface preparation requirements
- State building authorities — QBCC (QLD), Fair Trading NSW (NSW), VBA (VIC), BSCL (WA) — licensing requirements for painting contractors