Masonry Paint Calculator — Exterior Wall Paint Quantities

Our masonry paint calculator works by calculating the total exterior wall area, subtracting doors and windows, then dividing by the coverage rate for your surface texture. Exterior surfaces vary enormously in their paint absorption — rough pebbledash uses twice as much paint per m² as smooth render.

The formula

Litres needed = (Net wall area × Number of coats) ÷ Coverage rate per litre × Wastage factor

Net wall area = (Wall height × Wall length × Number of walls) − (Doors × 1.8 m²) − (Windows × 1.2 m²)

For example, a front wall 8m × 6m with smooth render, minus 1 door and 3 windows: Gross area = 48 m². Net area = 48 - 1.8 - 3.6 = 42.6 m². For 2 coats at 10 m²/L: 42.6 × 2 ÷ 10 = 8.5 L, plus 10% wastage = 9.4 L. You'd need 1 × 10L tin or 2 × 5L tins.

Coverage rates by surface texture

• Smooth Render: 10 m²/L — standard rendered walls with a flat finish (Dulux Weathershield / Sandtex Ultra Smooth)
• Textured Render: 7 m²/L — roughcast or stippled render finishes
• Pebbledash: 5 m²/L — heavily textured surface absorbs the most paint
• Bare Brick: 6 m²/L — porous brick absorbs significantly

These rates are calibrated to current Dulux Weathershield Smooth Masonry, Sandtex Ultra Smooth and Leyland Weatherproof Masonry technical datasheets. Two coats are standard for exterior masonry to achieve full coverage and protection. If the surface is powdery, apply stabilising solution first (coverage approximately 4 m²/L) and allow to dry before painting.