Paint calculator
How many litres a room needs, and which tins to buy. Enter the room's size; the answer updates as you type.
About 7.5 litres. Buy 1 × 5 L + 3 × 1 L.
- Walls, less doors and windows
- 33.1 m²
- Ceiling
- 12.0 m²
- Painted, per coat
- 45.1 m²
- Paint for 2 coats
- 7.5 L
For paint measured off your actual layout, room by room, with doors and windows where they really are, draw it in the designer: the quote there works it out as you draw.
How it works it out
The walls are the room’s perimeter times its height, less 1.89 m² for each door (a standard 900 × 2100 mm leaf) and 1.44 m² for each window (1200 × 1200 mm). Add the ceiling if you are painting it: it is often a quarter of the whole job, and easy to forget.
That area times the number of coats, divided by how far a litre goes, is the paint. Most emulsion covers 10–14 m² per litre per coat on a smooth, previously painted wall; the tin gives the figure for that paint. The tins suggested use 5 L for the bulk and 1 L to top up, switching to one more 5 L tin when that would take four or more small ones.
Questions
How much paint do I need for a bedroom?
A 4 × 3 m bedroom with a 2.6 m ceiling, one door and one window has about 33 m² of wall and 12 m² of ceiling. At 12 m² per litre, two coats of both take about 7.5 litres: one 5 L tin and three 1 L tins.
How many coats of paint do walls need?
Two coats is the norm, and the calculator starts there. A strong colour change, a dark colour over light (or the reverse), or new plaster may need a third, or a primer or sealer coat first.
Should I subtract doors and windows?
Yes, and the calculator does. On a small room they are a noticeable share of the wall, and leaving them in buys paint you will not use. Very large windows or sliding doors are better measured and entered as smaller wall dimensions.
Is the ceiling the same paint as the walls?
Usually not: ceiling paint is flat white and made not to drip. Untick "Paint the ceiling too" for the wall figure alone, then work out the ceiling separately from its area, length × width.