Paint Coverage per Litre

Every decorator has a story about a wall that drank a whole tin and still looked patchy. The usual explanation is bad luck; the real one is arithmetic. Paint coverage per litre — the number printed on the tin — is measured in conditions your room will never match, so a litre almost never goes as far at home as the label promises. This guide explains what coverage you actually get, surface by surface, and how to plan with figures that hold up. If you would rather skip straight to the numbers for your room, run it through our paint calculator first, then read on to see why its planning figures are deliberately cautious.

Why the number on the tin is optimistic

Manufacturers measure coverage on smooth, sealed, non-porous panels, applied evenly at a controlled thickness. It is an honest laboratory figure, but it describes a surface that barely exists in a real house. Real walls have pores, texture, patches of filler and old paint of varying absorbency, and all of that drinks a little of your first coat before any colour builds. The result is simple: on previously painted plaster you may get close to the claim, but on anything rougher or thirstier you will not. Plan with these working figures instead — emulsion at 10 to 12 square metres per litre, gloss and satinwood at 12 to 14, primer at about 10, and masonry paint at 6 to 10 depending on roughness.

Five things that eat your coverage

Coverage is not a property of the paint alone. It is what happens when a paint meets a surface, a colour and a method of application — and these five factors decide how far a litre really goes.

1. Porosity and new plaster

Bare plaster, filler and fresh repairs absorb the binder from your first coat, so that coat seals more than it covers. New plaster needs a mist coat — emulsion thinned with water — before the full coats, and even then the first full coat rarely reaches the tin’s figure. If a wall has never been painted, budget for the low end of the range and keep an extra coat’s worth in reserve.

2. Texture: stipple, brick and render

A flat wall measuring 10 square metres presents exactly 10 square metres of surface. A stippled, brick or rendered wall with the same measurements presents far more, because every bump, joint and hollow adds area the paint must cover. Heavy texture can cut coverage by a third, which is why masonry paint on rough render is planned at about 6 square metres per litre rather than the 10 its makers might suggest for smooth concrete.

3. Colour change

Hiding is coverage too. A deep red over pale cream, or white over dark blue, shows through until enough pigment builds up, and that usually means a third coat rather than a thinner second one. The litres per square metre barely change; the number of coats does, and the total paint climbs with it. A tinted primer or undercoat in a similar shade can often save a full coat of the more expensive topcoat.

4. Application method

The tool changes the maths. A roller is the standard the tin figures quietly assume. Spraying is fast and gives a smooth finish, but overspray and bounce-back waste paint, so expect spraying to use roughly 20 to 30 percent more than rolling the same wall. A brush lays paint on slightly more thriftily and suits small areas and cutting in, but it is slower, and heavy brush coats can drag. Whatever you use, two normal coats beat one thick one for both finish and predictability.

5. Coating thickness and hiding

Coverage figures assume a film just thick enough to hide. Lay the paint on generously — because the wall looks patchy, the colour is strong, or you are rushing the second coat — and every litre covers less. This is the quietest cause of all: nobody measures their film thickness, but everybody pays for it at the till.

Coverage by surface

As a starting point, match your surface to the row below, then adjust for the factors above.

Surface	Plan on	Note
Previously painted plaster	10-12 m² per litre	The best case, and the closest to the tin figure
New plaster	About 10 m² per litre, plus a mist coat	The first coat seals rather than covers
Wallpapered walls	8-10 m² per litre	Paint over paper only if it is sound and firmly stuck
Brick and block	6-8 m² per litre	Mortar joints and texture drink paint
Wood	12-14 m² per litre for gloss and satinwood	Smooth, sealed and usually primed first

If a wall matches two rows — new plaster with a strong colour going over it, say — plan on the worse figure. Planning pessimistically costs you a spare litre; planning optimistically costs a second trip to the shop and the risk of a mismatched batch.

How professionals plan

Professionals rarely run out, not because their walls behave better but because they plan differently. They measure the walls first instead of guessing from floor area. They use the planning figure for the surface in front of them, never the tin figure. They allow the extra coat for a problem wall at the estimating stage instead of hoping two coats will do. And they buy the whole job in one batch, because colour can vary very slightly between the batch numbers printed on tins, and a fresh tin bought mid-job can flash on a finished wall. You can copy the whole method in minutes: measure, choose your planning figure, and let the paint calculator turn it into the litres or gallons to buy. For the room-by-room method in feet and gallons, see how much paint do i need; for the metric room examples, see how many litres of paint per square metre.

A quick worked check

Take a single wall of 20 square metres. At the tin’s claimed 14 square metres per litre, the maths suggests 1.4 litres, so a 1.5 litre purchase looks safe. At a planning figure of 11 square metres per litre, the same wall needs 1.8 litres — and the 1.5 litres runs dry about three quarters of the way across the second coat. That gap, roughly half a litre on one wall, is exactly why people run out near the last wall of a room. Nothing went wrong; the plan was built on the wrong number. Run your own walls through the paint calculator using the planning figures above, and the gap closes.

Frequently asked questions