Paint Coverage Calculator
Estimate how many litres of paint and coats you need for a room.
How it works
Paint coverage is worked out from the total wall (and optionally ceiling) area you need to cover, divided by the paint's stated coverage rate — usually given in square metres per litre on the tin — and multiplied by the number of coats you plan to apply. Door and window openings are typically subtracted from the total area since you won't be painting them, though many people skip this step and end up over-ordering slightly, which isn't a large problem given paint's relatively long shelf life if resealed properly.
UK context
Coverage rates vary noticeably between paint types and finishes — matt emulsion typically covers more area per litre than a gloss or textured finish, and a porous, previously-unpainted surface (like new plaster) will absorb more paint on the first coat than a surface being repainted. Most manufacturers recommend two coats for a full, even finish, though a stark colour change (e.g. dark to light) sometimes needs a third.
Tips
- Always check the specific coverage rate stated on your chosen paint's packaging rather than assuming a generic figure — rates differ meaningfully between brands and finishes.
- Buy slightly more than the exact calculated amount, especially if colour-matching, since dye-lot variation between tins bought at different times can be noticeable on a wall.
- A first coat on bare plaster or previously unpainted surfaces often needs more paint than subsequent coats due to absorption — factor this in if you're painting new walls.
Frequently asked questions
How is paint coverage calculated?
Total wall area (minus door and window openings, if you're being precise) is divided by the paint's stated coverage rate per litre, then multiplied by the number of coats you're applying, to give the total litres needed.
Why does the same room need different amounts of paint depending on the brand?
Coverage rates vary by paint type, finish and formulation — always use the specific rate printed on your chosen product's packaging rather than a generic average, since the difference between brands can be significant.
Do I need to subtract doors and windows from my wall area?
For a precise estimate, yes — though many people skip this and simply order a small surplus instead, since leftover paint keeps reasonably well if resealed properly.
How many coats of paint do I actually need?
Two coats is standard for a full, even, opaque finish on most walls. A significant colour change, particularly going from a dark colour to a much lighter one, sometimes needs a third coat to fully cover the previous colour.
A quick note
Mix ratios, coverage rates and product yields vary by manufacturer and application — this page explains how the calculation works, not a substitute for product-specific technical guidance. Always check the manufacturer's data sheet, or consult a builder for structural or load-bearing work. See our full disclaimer.