Paint in litres: how much paint a room needs in metric
6 min read · Updated 2026-10-12 · BuildCalc
Paint is sold by volume and the container sizes are metric almost everywhere outside the United States — one, two and a half, five, ten and fifteen litres are the sizes you will meet. Working in litres from the start makes the tins line up with the answer, and avoids the awkward business of converting a square-foot coverage figure into litres after the fact.
From room size to square metres of wall
Paint goes on walls, so measure walls rather than floor. Add the four wall lengths, multiply by ceiling height, and you have gross wall area in square metres. A room 4 metres by 3.5 metres with a 2.5 metre ceiling has 2 × (4 + 3.5) × 2.5 = 37.5 square metres of wall.
Deduct the openings using roughly one square metre per door and half a square metre for an average window. Three openings in that room take away about 3 square metres, leaving 34.5 square metres to actually paint.
Coverage, coats, and the metric tin sizes
Coverage is printed on the tin and is quoted per litre. Ten square metres per litre is typical for interior emulsion on a smooth, previously painted surface; on bare plaster, fresh drywall or a textured wall the first coat can absorb far more, so assume the pessimistic end for a new surface.
Multiply the paintable area by the number of coats before dividing by coverage. Two coats is standard for a colour change, one is enough when refreshing the same colour. For 34.5 square metres at two coats and 10 square metres per litre, you need 6.9 litres — so a 10 litre tin, with something left for touch-ups.
Why a five litre tin is usually the better buy
Larger tins cost less per litre because the packaging and the tinting setup are amortised over more paint, and the price break often starts at five litres. The trade-off is that a large tin must be used within a reasonable time once opened; emulsion that has been thinned or contaminated is not reliable.
For a single room, ten litres is often more than you need and may not survive until the next job. For a whole floor or several rooms, five- or ten-litre tins are the economical choice. Measure first, then buy the smallest size that covers the job with a little to spare.
Ceilings, trim and the quantities people forget
If the ceiling is being painted too, add the ceiling area — length times width — and remember that it takes one coat more than a wall in a bathroom or kitchen where condensation is present. Skirting boards, door frames and window reveals are separate, usually in a harder-wearing trim paint, and are measured as length rather than area.
Finally, round up to a whole container and label anything you keep with the room and the date. A litre of correctly matched paint is the difference between a scuff you can fix and one you cannot.
Run your own numbers
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Common questions
How many litres of paint do I need for a room?
Divide the paintable wall area in square metres by the coverage per litre on the tin, then multiply by the number of coats. A 34.5 m² room at two coats and 10 m² per litre needs about 7 litres, so a 10 litre tin.
How much area does one litre of paint cover?
Around 10 square metres per litre on a smooth, previously painted wall. On bare plaster or fresh drywall the first coat covers considerably less.
Should I buy the largest tin available?
Not for one room. Large tins are cheaper per litre but opened paint does not keep indefinitely. Buy the smallest size that covers the job with a little spare.
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