How Much Paint Do I Need For A Room?

It depends heavily on the room's size, how many doors and windows it has, and how many coats you're doing, which is why a single "average room" figure is unreliable. As a rough anchor, a typical UK box bedroom (around 4m x 3.5m with a 2.4m ceiling, one door, one window) needs roughly 5-6 litres for two coats of standard emulsion at the default 12 m²/litre coverage rate - enter your own room's numbers above for an exact figure.

Manufacturers often quote a spreading rate of 14-16 m² per litre for standard emulsion on a smooth surface (Dulux's own Easycare product pages and Crown's Breatheasy state figures in this range). In practice, previously painted or lightly textured walls tend to cover less, which is why this calculator defaults to a more conservative 12 m²/litre - check the figure printed on your own tin and adjust the Paint Coverage Rate field if it's different.

That's a personal choice, but if you're doing it, set "Include Ceiling?" to Yes so its area (length x width) is added to your paintable total. This calculator assumes ceiling paint covers at the same rate as your wall emulsion, which is a simplification - dedicated ceiling paints sometimes have a slightly different (often higher, flatter) coverage rate, so check your specific product if you're using one.

Two coats is the standard recommendation for a full colour change, new plaster, or when painting over a noticeably different existing colour, because a single coat rarely gives even, solid coverage. One coat can be enough for a like-for-like refresh in the same or a very similar colour. A third coat is sometimes needed for a light colour over a dark one, or for very porous/new plaster - use the coats scenario table to compare all three.

Because for a shopping-list estimate, a fixed average (1.8 m² per door, 1.2 m² per window, both including the frame) gets you close enough to the right tin size without a room-by-room opening survey. If your room has unusually large openings - a bay window, patio doors, or an oversized door - the calculator will slightly overestimate the paint you need, which is the safer direction to be wrong in.

Nothing in the underlying maths - the difference is which units and market the calculator is built for. This tool works entirely in metres and litres for UK rooms and UK retail tin sizes (1L/2.5L/5L); CoryVu's separate Paint Coverage Calculator (Square Feet) is built around US units (square feet and gallons) instead.

Not directly - coverage rate and coat count are both things you control to compensate for a big colour change. If you're going from a dark or saturated colour to a much lighter one, budget for a third coat (or a dedicated "one-coat" high-opacity product, or a grey/coloured primer first) rather than assuming the standard two-coat figure will fully hide the old colour.

The tin-rounding in this calculator already builds in a small buffer, since litres required rarely divides evenly into 1L/2.5L/5L tins. If your walls are heavily textured, very porous, or you're painting a strong, saturated colour that typically needs an extra coat, consider rounding up to the next tin size manually rather than cutting it fine.

The calculator assumes one simple rectangular room. For an L-shaped, open-plan, or multi-room space, split it into rectangular sections, run the calculator separately for each, and add the litres together - trying to average an irregular shape into one length/width entry will under- or over-estimate the result.

Lower than the smooth-surface figure printed on the tin - textured (e.g. Artex-style) or heavily porous surfaces commonly need 20-30% more paint. If your walls fall into this category, reduce the Paint Coverage Rate field from the 12 m²/litre default to somewhere around 8-10 m²/litre to get a more realistic (higher) litres estimate.

No - masonry paint for exterior walls typically has a different, usually lower, coverage rate than interior emulsion, and this calculator's defaults are built around standard interior emulsion. If you're painting an exterior wall, use the coverage rate printed on your masonry paint tin instead of the 12 m²/litre default, and see CoryVu's exterior render coverage calculator if you're rendering rather than just painting.

The calculator picks the largest tins first and tops up with smaller sizes to avoid excessive leftover paint, which can occasionally suggest more tins than buying one larger size and accepting more waste. Both are valid choices - compare the total cost and leftover-paint trade-off for your specific retailer's pricing before buying, especially if a single larger tin works out cheaper per litre.

Yes, if you enter a price per litre in the optional field, the Results Dashboard and Smart Insights will show an estimated total cost based on the tins suggested. Leave it blank to see quantities only - no price is assumed by default.

No - it's a materials-quantity estimate built from standard reference figures (coverage rate, door/window deduction sizes), not a measured take-off of your specific room. Use it to get a confident ballpark before buying, but a specific project - especially a large or unusually shaped room - will benefit from measuring your actual openings and checking the coverage figure on your chosen paint.