How much exterior wall paint do you need?

At 5 m²/L and two coats on a normal render: 100 × 2 ÷ 5 = 40 liters before waste and surface factor. Add 10% waste → ~44 L. Very rough brick or porous block can push past 50 L.

On bare render or after stripping failing paint, yes — primer stabilizes suction and improves adhesion. This calculator sizes finish coats; add primer separately (often similar liters to one full coat) or use the metal-primer tool if you are on galvanized elements.

Only inside the temperature and humidity window on the label — typically +5 to +25 °C and dry weather. Cold slows cure and can cause flaking; rain within 24 h of application is a common failure mode. Buy slightly extra so you are not reopening partial cans next season.

Large flat render: airless sprayer is fastest but needs skill and masking. Textured surfaces and DIY renovators usually roll — slower but less overspray waste. Spraying often needs +15% material in the waste field.