Paint Coverage by Surface Type
Paint coverage is not a single number — it depends on the surface, the paint type, the colour change and the application method. A tin that covers 12 m² per litre on a sealed wall may cover only 6 m² on bare plaster, and a dark wall painted white needs three coats where a refresh needs one. This guide explains how surface type drives coverage so the Paint Quantity Calculator’s result matches your real job.
Pair it with the Paint Quantity Calculator, which lets you set the coverage figure to match your surface and paint. The core idea is that coverage is a property of the surface-and-paint combination, not of the paint alone.
In detail
Previously painted walls: the baseline
A sound, previously painted wall is the easiest surface: emulsion covers about 10–12 m² per litre per coat, and a refresh of the same colour often needs one coat. A colour change usually needs two coats, and a light colour over a dark one may need three. The wall should be clean and dry, with any gloss sanded to a key. This is the baseline the Paint Quantity Calculator assumes by default (10 m²/L, two coats), and it is the most common indoor job.
Bare plaster and new drywall: the thirsty surfaces
New plaster and bare drywall are highly porous and suck up paint, dropping coverage to about 6–8 m² per litre on the first coat. A mist coat — a thinned first coat of emulsion, about 10% water — is essential to seal the plaster before the full coats; without it, the paint sits on the surface and patches. After the mist coat, coverage returns to near-normal for the finish coats. Budget for an extra coat and lower coverage on any bare plaster surface.
Wood and metal: different paint, different coverage
Wood and metal use gloss, eggshell or specialist enamels rather than emulsion, and coverage runs about 12–15 m² per litre — but they need a primer on bare surfaces, which is a separate product with its own coverage. Bare wood should be knotted and primed; previously painted wood should be sanded to a key. Metal needs a rust-inhibiting primer on bare areas. These surfaces typically need two to three coats for a durable finish, and the primer counts as a separate quantity to calculate.
Texture, colour and application method
Textured surfaces (artex, rough plaster) have a greater effective area than their flat dimensions and reduce coverage by 20–30%. A dramatic colour change — light over dark, or a strong accent colour — needs more coats, sometimes with a tinted primer underneath. Roller application covers slightly more than brush because it lays the paint on more evenly, while spraying can cover more still but wastes overspray. The coverage figure on the tin is usually for a roller on a smooth surface, so adjust down for texture or brush work.
Setting the coverage in the calculator
The Paint Quantity Calculator has a coverage field (m² per litre per coat) and a coats field, so you can match the surface. For a refresh of a painted wall, use 10–12 m²/L and one or two coats. For bare plaster, use 7 m²/L and three coats (including the mist coat). For textured surfaces, drop the coverage by 25%. Always check the coverage printed on your specific tin — it varies by product and is the most reliable figure for that paint on a standard surface.
Frequently asked questions
- What coverage should I enter for bare plaster?
- About 7 m² per litre for the first (mist) coat, because bare plaster is very porous. After a thinned mist coat seals it, the finish coats cover closer to 10–12 m²/L. Budget for three coats total on new plaster.
- How does a colour change affect the number of coats?
- A refresh of the same colour often needs one coat. A colour change usually needs two, and a light colour over a dark one may need three, sometimes with a tinted primer. The calculator’s coats field lets you set this directly.
- Does texture reduce coverage?
- Yes. A textured surface (artex, rough plaster) has a greater effective area than its flat dimensions, so coverage drops by about 20–30%. Reduce the coverage figure you enter in the calculator accordingly.
- What about primer — is that included?
- No. Primer is a separate product with its own coverage. On bare wood or metal, calculate the primer quantity separately using its tin’s coverage figure, then the topcoat quantity using the paint’s figure. The calculator handles one product at a time.
Related calculators
Concept guide based on standard paint coverage practice. Typical coverage: emulsion 10–12 m²/L on painted walls, 6–8 m²/L on bare plaster, gloss 12–15 m²/L on wood/metal. Always check the tin. Last updated: September 2026.
These guides are provided for general information only and do not constitute financial advice. Exchange rates, tax rules, customs allowances and tipping customs vary by country, provider and over time. Always confirm critical figures with the relevant authority or a qualified adviser before acting on anything here.