How much paint for a 4x4 metre room?

Walls in a 4 × 4 m room with a 2.4 m ceiling come to about 38 m². At two coats and 12 m² per litre that is roughly 6.4 litres, plus waste — so a 10 litre tin, with some left for touch-ups. The ceiling adds about 16 m² — roughly 1.3 litres at one coat, or 2.7 at two.

How many coats do I need?

Two, on almost anything previously painted in a similar colour. Three when you are going light over a strong dark, or covering a patch repair that will otherwise flash. New plasterboard wants a sealer plus two.

How much extra should I allow for waste?

Five to ten percent on a straightforward job. More on a cut-up job with lots of small rooms, because a bigger share of each tin ends up in the tray and on the brush.

All guides

How much paint do I need?

Put the room in and it works out the litres, then the cheapest combination of tins to cover it.

3 min read

Work out the paint

Runs in your browser. Nothing is sent anywhere and nothing is stored.

Room length (m)

Room width (m)

Ceiling height (m)

Painting

Coats

Spreading rate (m² per litre)

12 is typical on sound painted walls. Use your own if you know it.

Waste allowance (%)

Area to cover

38.4 m²

Paint needed

6.91 L

6.4 L before waste

Cheapest tins

1 × 4 L + 3 × 1 L

7 L purchased

Tin sizes are the common Australian and New Zealand set (1, 4, 10 and 15 litre). The combination shown is the cheapest that covers the volume, which is not always the fewest tins.

The arithmetic behind it

Paint quantity is one of the few things on a job that is genuinely a formula. Area, times coats, divided by how far a litre goes, plus an allowance for what ends up in the roller tray and on the drop sheets.

The calculator above runs exactly that, using the same code that prices real jobs in this app. Nothing is rounded up to sell you more paint.

Area × coats ÷ coverage, plus waste. Everything else is a judgement about which of those four numbers to use.

What coverage rate to use

A litre of wall paint covers somewhere between 10 and 14 square metres on a sound, previously painted surface. The spread you get is real and it depends on things you can see before you start.

New plasterboard drinks the first coat — treat a sealer coat as covering less. A heavy texture, brickwork or render can halve it. Going light over dark is a coats problem rather than a coverage problem: the litres per coat stay the same, you just need more coats.

Surface	Roughly, per litre
Smooth previously painted wall	12–14 m²
New plasterboard, sealer coat	8–10 m²
Light texture	9–11 m²
Render or brick	5–8 m²
Ceilings, flat white	12–14 m²

Manufacturer figures are measured on ideal surfaces. Yours will be lower. If you have kept records of past jobs, use your own number instead — it is the more accurate one.

Do you subtract the windows and doors?

For a normal room, no. A standard door and one window come to roughly four square metres between them, which on a typical lounge is inside the waste allowance you were carrying anyway.

Subtract them when the openings are genuinely large — a wall that is mostly glass, a set of stacking doors, a stairwell void. At that point they are not a rounding error, they are a chunk of the wall.

Why tin sizes matter more than litres

Needing 11 litres does not mean buying 11 litres. It means buying the cheapest set of tins that gets you to 11, and that is rarely the obvious one — a single 15 litre pail often beats a 10 plus a 4 plus a 1, and sometimes it does not.

The calculator solves that properly rather than rounding up to the next size, because paint is usually the largest material line on a job and the difference shows up on every one.

Common questions

How much paint for a 4x4 metre room?: Walls in a 4 × 4 m room with a 2.4 m ceiling come to about 38 m². At two coats and 12 m² per litre that is roughly 6.4 litres, plus waste — so a 10 litre tin, with some left for touch-ups. The ceiling adds about 16 m² — roughly 1.3 litres at one coat, or 2.7 at two.
How many coats do I need?: Two, on almost anything previously painted in a similar colour. Three when you are going light over a strong dark, or covering a patch repair that will otherwise flash. New plasterboard wants a sealer plus two.
How much extra should I allow for waste?: Five to ten percent on a straightforward job. More on a cut-up job with lots of small rooms, because a bigger share of each tin ends up in the tray and on the brush.