Paint needed
5.1 L
30.2 m² to paint · buy 1 × 5 L + 1 × 2.5 L
Your figures, your sums - nothing is sent anywhere. Doors count as 1.9 m², windows as 1.5 m². Fresh plaster and strong colour changes take more.
How much paint a room needs
Work out the wall area: the distance round the room (twice the length plus twice the width) multiplied by the height. Take off about 1.9 m² for each door and 1.5 m² for each window.
Multiply by the number of coats, then divide by how much one litre covers. Most emulsions cover 10 to 14 m² a litre; the tin states the figure.
A worked example
A room 4 m × 3 m with a 2.4 m ceiling height has 33.6 m² of wall. With one door and one window taken off, that leaves 30.2 m².
Two coats is 60.4 m². At 12 m² a litre you need 5.1 litres, so one 5 litre tin plus a 2.5 litre tin.
Painting the ceiling too adds 12 m² (4 × 3). Two coats over walls and ceiling is about 7.1 litres, so a 5 litre and a 2.5 litre tin again.
What changes the amount
Bare plaster, rough or textured walls and porous surfaces soak up more paint. New plaster needs a thinned mist coat before the first full coat.
A strong colour change, or covering a dark wall with a light colour, often needs a third coat. Ceilings are usually matt white and take two.
Skirting, doors and window frames are normally a different paint (satin or gloss) and are not included in the wall figure.
Common mistakes
Forgetting that the coverage on the tin is per coat. Two coats needs twice the litres.
Not rounding up to whole tins, or buying tins from different batches for the same wall, where the shade can differ slightly.
Forgetting the extras: masking tape, dust sheets, filler, caulk and primer all belong on the materials list.
JobGuard puts the materials on your quote with your markup and suggests what is easy to miss.
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Questions
How much paint do I need for a room?
Add up the wall area (each wall’s length × height), take off doors and windows, times the coats, then divide by the coverage on the tin. A 4 × 3 m room with 2.4 m walls takes about 5 litres for two coats.
How much paint do I need for a ceiling?
Ceiling area is length × width. A 4 × 3 m ceiling is 12 m², which takes about 1.5 litres for two coats at 10 m² per litre. Use ceiling paint, it is thicker and spatters less.
How many coats?
Two is usual. New plaster needs a mist coat first, and a strong colour change or a dark wall can need a third.
Should I add some spare?
A little: rough walls soak up more than the tin says, and a spare half-tin is handy for touch-ups. Put it on the quote so it is paid for.