How much paint per square metre?
About 12 m² per litre per coat on a previously painted smooth wall. The figure drops to 10 on new plaster, 8 on textured and 6 on bare masonry — and the first coat on a thirsty surface takes more than the ones after it, which is the part most estimates leave out.
Quick answer
About 12 m² per litre per coat on a previously painted smooth wall. The rate falls to 10 m² on new plaster or plasterboard, 8 on textured, and 6 on bare render or masonry; joinery and metal run at 14. On an unprimed porous surface the first coat takes up to a third more than the ones after it, because the substrate absorbs part of it. A 4 × 3 m room has about 29 m² of wall after deducting a door and a window, so two coats is 5 litres on previously painted walls and 12 on bare masonry.
| Surface | m² per litre | First coat | Later coats | Two coats |
|---|---|---|---|---|
| Previously painted, smooth | 12.0 | 2.42 L | 2.42 L | 5.0 L |
| New plaster or skim (sealed) | 10.0 | 3.87 L | 2.90 L | 7.0 L |
| New plasterboard | 10.0 | 3.87 L | 2.90 L | 7.0 L |
| Textured, artex, heavy roll | 8.0 | 4.27 L | 3.63 L | 8.0 L |
| Render, brick, rough masonry | 6.0 | 6.91 L | 4.84 L | 12.0 L |
| Wood trim, doors, joinery | 14.0 | 2.44 L | 2.07 L | 5.0 L |
| Metal, radiators, railings | 14.0 | 2.07 L | 2.07 L | 4.5 L |
The same room costs you 5 litres over a previously painted wall and 12 over bare masonry. That is the entire reason a single “paint per square metre” number is not usable: the substrate swings it by more than a factor of two.
The first coat is not the same as the rest
On a porous surface the first coat is partly absorbed rather than left on the surface as film. New plaster drinks about a quarter of it; bare masonry closer to a third. So the first coat on new plaster is 3.87 L where the second is 2.90 L — a third more, for the identical area.
Priming removes that penalty, which is the real argument for it. A primer or mist coat is cheaper per litre than a finish paint and seals the surface, so the finish coats then both go on at the full rate. On bare masonry, priming saves about two litres of finish paint on this one small room; on new plaster it is not optional at all, because unsealed plaster will peel the paint off in sheets.
By room size
| Room | Wall area | Walls | Tins | Walls + ceiling | Tins |
|---|---|---|---|---|---|
| 2 × 2 m | 14.6 m² | 2.5 L | 1 × 2.5 L | 3.5 L | 1 × 2.5 L + 1 × 1 L |
| 3 × 3 m | 24.2 m² | 4.5 L | 1 × 5 L | 6.0 L | 1 × 5 L + 1 × 1 L |
| 3 × 4 m | 29.0 m² | 5.0 L | 1 × 5 L | 7.0 L | 1 × 10 L |
| 4 × 4 m | 33.8 m² | 6.0 L | 1 × 5 L + 1 × 1 L | 8.5 L | 1 × 10 L |
| 4 × 5 m | 38.6 m² | 6.5 L | 1 × 10 L | 10.0 L | 1 × 10 L |
| 5 × 5 m | 43.4 m² | 7.5 L | 1 × 5 L + 1 × 2.5 L | 11.5 L | 1 × 10 L + 1 × 2.5 L |
| 5 × 6 m | 48.2 m² | 8.5 L | 1 × 10 L | 13.5 L | 1 × 10 L + 1 × 2.5 L + 1 × 1 L |
The litres are what the paint actually has to cover; the tins are what is on the shelf, and the two rarely land on each other. Where they do not, there is a real choice to make and it is not the obvious one. A 4 × 5 m room needs 6.5 litres, and 1 × 2.5 L + 4 × 1 L hits that exactly with nothing left over — but that is five tins, and a 1 litre tin can cost three times a 10 litre one per litre. One 10 litre tin is almost always the cheaper buy despite wasting three and a half litres. The tins above are the plan that wins on that reasoning; the calculator shows both and states the trade rather than deciding for you.
Why your tin claims better than this
Tin figures are measured on a sealed, smooth, primed panel at a controlled film thickness, in a laboratory. A roller on a real wall lays a thicker and less even film, some paint stays in the tray, and more stays in the sleeve. Treat the number on the tin as a ceiling rather than an estimate. If you want to use it anyway, the calculator has a coverage box — type it in and it will use yours.
What the figures do not include
- A third coat. Going dark over light, or using a saturated red, orange or yellow, plan for three. Those pigments have poor opacity and are the classic four-coat disasters. A grey-tinted primer under a deep colour usually saves a whole finish coat.
- Cutting in and touching up. Small on a big room, not small on a small one. Round up to the tin, which you are doing anyway.
- Radiator backs, window reveals and the inside of a cupboard. Easy to forget at measuring time and not at painting time.
- Trim and skirting as separate products. Joinery takes a satin or gloss at 14 m²/L, and one litre goes a long way. The usual mistake is buying far too much.
Common questions
How many square metres does a 5 litre tin cover?
About 60 m² in one coat on a previously painted smooth wall, so 30 m² in two coats — roughly one average bedroom's walls. On sealed new plaster it is 50 m² a coat, and on bare masonry 30. Those are the straight coverage rates; if the surface is unprimed, the first coat eats more than its share, which is the point of the table above rather than a footnote to it.
Do I measure the ceiling height or the wall height?
Floor to ceiling, which is the same thing unless there is coving. The calculator takes room length, width and height and works the perimeter out, so you do not measure four walls separately — and it deducts a standard door and whatever window area you give it, rather than pretending the openings are not there.
What about a mist coat on new plaster?
It counts as your primer. The traditional mist coat is the same emulsion thinned roughly 30% with water; it seals the plaster so the finish coats do not peel. Tick the primer option and the calculator allows for it at about 11 m² per litre and removes the first-coat absorption penalty from the finish paint.
Is one litre per 12 square metres a safe number to plan with?
For a repaint on sound previously painted walls, yes. For anything bare, porous, textured or deeply coloured, no — those are the four cases where the single figure is wrong, and between them they cover most of the reasons anyone is painting in the first place.
Related
- Paint calculator — your room, your surface, with primer and trim priced separately
- Paint coverage rates reference — the full table and where each rate comes from
- Painting a replastered room — the worked example, including the mist coat
- These tables as JSON — with the inputs that produced each row
Last reviewed 2026-10-17. Litres and tin plans generated from the paint calculator on this site; a test re-checks every figure above against the live tool on each build.
Sources and confidence
Every figure used on this page, what kind of figure it is, and where it came from. Figures marked as working estimates have no single authority behind them — they are the ones to check against your own supplier.
| Figure | Kind | Source | Note |
|---|---|---|---|
| Every litre figure and tin plan in the tables | Derived | Generated from this site's paint calculator | Produced by driving the calculator across every surface and room size listed. A test re-checks each cell against the live tool on every build. |
| Practical coverage rates per litre, and the first-coat absorption factors | Working estimate | no primary source consulted | Practical rates, deliberately below the figures printed on tins, which are measured in a laboratory on a sealed panel. See the paint coverage rates reference. |
| Standard door and window deductions | Working estimate | no primary source consulted | 830 × 2030 mm door, 1.44 m² window. Measure your own if they are unusual. |
| Mist coat at about 11 m² per litre | Working estimate | no primary source consulted | Emulsion thinned roughly 30% with water. The thinning ratio varies by paint. |
Derived Calculated from geometry. The formula is on this page. Published From a manufacturer data sheet or published standard, cited below. Working estimate Trade practice, rounded up. No single authority; the weakest category here.