How much paint per m²: what the data sheet says and what a room actually takes

Paint calculators ask for two numbers, the area and the coverage, and give you litres. The division is the easy part. What almost always goes wrong is the two numbers you feed in: the floor area instead of the wall area, and the coverage on the tin taken as a promise.

We have read the data sheets of three interior emulsion paints to see what they really say, and worked the sum through on an example bedroom.

What the coverage on the data sheet means

It is what one litre covers in one coat, and it is hardly ever a single number: it is a range. The data sheet for a mid-range paint gives “Coverage (m2/L) 8 - 12”; the one for a budget paint, “6-8 m²/L per coat”. Between the paint that goes furthest and the one that goes least far, a factor of two.

It is also a laboratory figure. The first sheet warns that its figures are a guide, not binding, and that they are “based on laboratory tests carried out at 20ºC”. The sheet for a one-coat paint, from 2007, puts it even more plainly: “10-12 m2/lt. per coat on smooth surfaces”. A real wall is rarely as smooth, or soaks up as little, as the one in the test.

There is another figure on the mid-range sheet that helps explain the range. Its opacity, how much it hides of what is underneath, reaches the best class at a coverage of “4.3 m2/litre corresponding to 2 coats of paint”. In other words: with two coats, one litre for 4.3 m² of wall. Spread it further and it hides less. What those classes are, and which to ask for in each room, we cover in painting walls and ceilings.

The area: walls and ceiling, not floor

The other number in the sum. What gets painted in a room is its four walls and its ceiling, and that measures quite a lot more than the floor. We take the main bedroom of the example flat on our page on the cost of painting a flat: 4 × 3.5 m of floor, 2.5 m ceilings. Its walls add up to 37.5 m² and its ceiling to 14: 51.5 m² to paint on 14 of floor. And that is without taking off the door or the window. To measure yours, wall by wall, there is our area calculator.

The two coats

Both current data sheets count on two: the mid-range one recommends a minimum of two finishing coats and the budget one says “Number of coats: 2”. Even the one-coat paint, made for a single coat, admits that “in some cases, depending on the substrate, a second coat is needed”. So the bedroom’s 51.5 m² are, as far as paint goes, 103.

Dividing those 103 m² by the coverage on each sheet:

• Mid-range paint (8 to 12 m²/L per coat): between 8.6 and 12.9 litres.
• Budget paint (6 to 8 m²/L per coat): between 12.9 and 17.2 litres.
• At the coverage the mid-range paint uses to measure its opacity (4.3 m² per litre over two coats): 12 litres.

The lesson speaks for itself: price per litre is no way to compare two paints unless you look at how many metres each litre covers. One that goes half as far needs twice as many tins.

What makes you use more

New plaster

A filled chase, a new partition or a freshly plastered wall soak paint up. The budget sheet asks for “1 coat of water-based primer” on new plaster before the paint, and the mid-range one for a coat of sealer, “reducing absorption and making the subsequent application of paint easier”. The difference shows on the same sheet: one of its sealers covers 15 to 20 m² per litre on an already painted surface, and 5 to 15 on plaster. It is extra paint, to be added on.

A change of colour, and patched walls

When the wall is not the same all over, the mid-range sheet recommends another coat first: “If the surface to be painted has an uneven appearance (different materials, areas of different colours, repairs, etc.) a coat of an opaque acrylic primer in the chosen colour is recommended”.

A wall that is not smooth

The coverage on the data sheet is measured on a smooth surface. A textured wall, gotelé (the spattered texture common on Spanish walls) for example, has more surface than the tape measure says and takes more paint. If yours is not smooth, do the sum with the low end of the range.

On the coast, before you buy

Both current data sheets ask for a sound wall: the mid-range one, surfaces “free of dust, grease, salt deposits”, and the budget one, removing “efflorescence, soluble salts” first. Here that is no small detail. If salt is coming through at the bottom of the wall, paint will not fix it and will lift with it. Where it comes from and what to do first, in our article on salt deposits. And if you are painting in summer, check the conditions on the sheet: the budget one asks for temperatures below 25 °C, and the mid-range one advises against “the hottest hours”.

The sum, in three steps

1. Measure walls and ceiling, room by room. Not the floor area, nor the one in the listing.
2. Multiply by the coats: two, unless the data sheet says otherwise.
3. Divide by your paint’s coverage, the one on its data sheet, and take the low end if the wall is new, rough or changing colour. Primer on top.

If you would rather we did it, send us the measurements and the quote comes with the area counted and the paint named.

Frequently asked questions

Sources

• Isaval, ficha técnica de M14 Pinmat (version 6, 12 February 2026).
• Leroy Merlin, ficha técnica de «Pintura interior Económica» (REV 9/1901).
• Valentine, ficha técnica de «1 Sola Capa» (January 2007 edition).

Quotations from Spanish-language documents are our own translations.