Repaint a room — a chain reaction

Measure the walls, not the floor

Paint covers wall area, which is the perimeter times the height — nothing to do with floor area. A 4 × 5 m room at 2.7 m high has the wall area below once a door and a window are taken out.

Wall area45.3 m²

Two coats9.1 litres

2.5 L tins4

Rule of thumbEmulsion covers about 11 m² per litre per coat on primed walls. Bare plaster drinks the first coat — budget more.

Open Paint Coverage Calculator with these numbers →

Add the ceiling only if you are doing it

The ceiling is usually the same area as the floor and is a different paint. Toggle it on and the tool adds it as its own line rather than folding it into the wall figure.

Ceiling area20 m²

Different paintusually matt white

Rule of thumbCutting in takes about as long as rolling the whole rest of the room. Plan the time, not just the paint.

Open Paint Coverage Calculator with these numbers →

Mix a colour you can mix again

Eyeballing a tint means you can never repeat it. Mixing by volume ratio means you can — scale the same ratio up and get the same colour, which matters the day you need to patch one wall.

Mix byvolume, not eye

Recordthe ratio, not the result

Rule of thumbPaint dries darker than it looks wet. Judge a colour only once a test patch is properly dry.

Open Paint Colour Mixing →

Cost the job before you buy

Tins come in fixed sizes, so the honest cost is the number of tins rounded up, not the litres. Put your actual tin price in and the tool prices the job the way the checkout will.

Tins needed4

At £8 per 2.5 L£32

Rule of thumbBuy one extra tin of a mixed colour. Re-mixing a match later costs far more than the spare tin does.

Open Paint Coverage Calculator with these numbers →

Measure the walls, not the floor

Add the ceiling only if you are doing it

Mix a colour you can mix again

Cost the job before you buy

Four numbers and a repeatable colour