Primer calculator — surface area & whole tins

Keep primer separate from your finishing paint

Use only the surfaces that will actually be primed. Apply the primer’s own coverage and number of coats. Spot priming can be entered as a measured area; whole-room priming uses the full selected surface area.

For example, 20 m² at 10 m² per litre and one coat needs two litres. Porosity, stains, preparation and the current coating instructions determine the actual process.

Does “paint + primer” remove this step?

A product name alone does not establish whether your surface needs a separate primer. Read the preparation guidance for both coatings. The calculator does not approve a primer/topcoat pairing.

How much area would 20 litres of primer cover?

At an illustrative 10 m² per litre, 20 litres covers 200 m² for one coat or 100 m² for two coats before extra allowance. This is arithmetic using an assumed label rate, not a verified 20-litre product offer. Use the coverage and coats stated for your exact primer.

Coverage and coats change the result

Manufacturer ranges use their lower coverage value by default. A quoted “up to” coverage is not a guarantee on every surface. Check porosity, colour change, application method and preparation; adjust the form to your current label.