Exterior Paint Calculator – Free Estimate for Outdoor Surfaces
Painting the outside of your home? Get an exact litre estimate for any exterior surface — render, weatherboard, brick, and more.
Free Paint Calculator
Paint Calculator
Enter your wall dimensions below
Calculating Exterior Paint
Exterior paint calculations follow the same core formula as interior — Wall Area ÷ Coverage Rate × Coats = Litres Required — but exterior surfaces typically absorb more paint due to texture, weathering, and porosity. Most exterior paints cover 6–10 m² per litre, compared to 10–12 m²/L for smooth interior walls.
When estimating exterior paint, include all external walls, fascia boards, eaves, and any feature areas. Exterior jobs usually require 2 coats of paint over a properly prepared surface, and sometimes a coat of primer on bare or heavily weathered areas.
Exterior Surface Coverage Rates
| Surface | Coverage per Litre | Coats | Notes |
|---|---|---|---|
| Smooth render / stucco | 8–10 m²/L | 2 | Best coverage outdoors |
| Rough / sand render | 5–7 m²/L | 2 | High absorption |
| Weatherboard / timber | 7–9 m²/L | 2–3 | Oil-based or acrylic |
| Fibre cement (Hardiplank) | 8–10 m²/L | 2 | Seal before painting |
| Brick (painted) | 6–8 m²/L | 2 | Elastomeric recommended |
| Brick (unpainted) | 4–6 m²/L | 2–3 | Must prime first |
| Metal cladding | 10–12 m²/L | 2 | Use metal primer |
Exterior Painting Conditions & Preparation
When to Paint Exteriors
Ideal conditions are 15–25°C with low humidity and no rain forecast for 48 hours. Avoid painting in direct midday sun — the heat causes paint to dry too fast, leaving brush marks.
Surface Preparation
Pressure wash and allow to fully dry (24–48 hours). Sand any flaking or peeling paint back to a firm edge. Apply exterior primer to all bare patches before topcoating.
Choosing Exterior Paint
100% acrylic exterior paint is the gold standard. It flexes with temperature changes, resists UV fading, and repels moisture. Quality exterior paint should last 7–12 years before repainting.
Exterior Painting Tips
Work from top to bottom — start with eaves, fascia, and upper walls, then work down
Use a long-nap roller (12–18mm) on textured render and rough masonry
Apply two thin coats rather than one thick coat for better coverage and durability
Always prime bare timber and metal with an appropriate exterior primer
Check the weather forecast — paint needs minimum 4–6 hours dry time before rain
Upgrade to Paint Pro Calc Pro
Unlock professional tools including multi-room calculations, cost estimation, quotes, invoices, and project management.
From $2.99/month · No credit card required for trial