Exterior Paint Calculator — House Walls and Cladding

Exterior paint projects need accurate estimates — running out and stopping part-way through a wall creates visible lap marks and colour mismatches. Enter your house perimeter and wall height to get a precise litre count.

Enter your measurements

Wall perimeter(m)

Measure around the outside of the building at wall height.

Wall height(m)

Number of doors

Number of windows

Coats of paint

Coverage per litre(m²/L)

Exterior masonry paint typically covers 8–12 m²/L on smooth surfaces.

Waste allowance(%)

Can size(L)

How we calculate

Wall area = perimeter × height. Deduct 1.9 m² per door, 1.2 m² per window. Paint = (paintable area ÷ coverage) × coats × (1 + waste %). Cans = ⌈litres ÷ can size⌉.

Worked example

House with 30 m perimeter, 2.8 m walls, 2 doors, 6 windows, 2 coats, 10 m²/L, 15% waste. Wall area = 84 m², paintable ≈ 73.7 m². Paint ≈ 17 L → 4 × 5 L cans.

Common mistakes

•Using interior paint outside — it lacks UV and weather resistance.
•Underestimating rough or textured masonry which absorbs 20–30% more paint.
•Skipping primer on bare render or over a chalky surface.
•Painting in direct sunlight — paint dries too fast and leaves streaks.

How we calculate

Worked example

Common mistakes

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