Paint Calculator
Type the room size, the number of doors and windows and the coats you want. You get the litres needed and the tin sizes that cover it with the least left over.
This is an estimate. The coverage printed on the tin is the number to trust.
Worked examples
A small bedroom
4 m by 3 m, 2.4 m high, one door, one window, two coats
5.1 litres, so a 5 litre and a 1 litre tin
Walls are 33.6 square metres, less 3 square metres for the door and window, at 12 square metres a litre.
About Paint Calculator
A paint calculator works out how much paint to buy for a room so that you do not run out halfway down a wall or end up with several half-full tins. The amount depends on the area you are painting, the number of coats and how far one litre of your paint goes. Enter the length, width and height of the room and the calculator finds the wall area, takes off doors and windows, and gives the litres you need.
It then suggests tin sizes. Paint is sold in 1, 2.5, 5 and 10 litre tins, and the tool finds the combination that covers what you need, with a 10% allowance for touching up, using the least paint over. The coverage printed on your tin is the number to use, so change the default of 12 square metres a litre if the tin says something different.
How to use Paint Calculator
- Enter the length, width and ceiling height of the room.
- Enter the number of doors and windows, and the number of coats.
- Check the coverage on your tin and change it if it is different. Tick the box to paint the ceiling too.
- Read the litres needed and the tins to buy.
Common uses
- Repainting a bedroom or living room
- Comparing the cost of two paints
- Planning a decorating budget
- Ordering for a rental property
Frequently asked questions
How much paint do I need for a 4 m by 3.5 m room?
With a height of 2.4 m the walls are 36 square metres. After one door and one window that is 33 square metres, and two coats at 12 square metres a litre is 5.5 litres. With 10% spare you would buy a little over 6 litres, and the tool suggests the tins that cover it.
How far does a litre of paint go?
Most emulsion covers 10 to 14 square metres a litre on a smooth, sealed wall. Rough or porous surfaces take less. The coverage is printed on the tin, so use that.
Do I need to paint the ceiling separately?
Ceilings usually use the same paint type but are often white. Tick the ceiling box to add it to the total, or work it out as a separate job if you will use a different colour.
How many coats of paint will I need?
Two coats is normal. Going from a dark colour to a light one, or painting over bare plaster, may need more, and a primer or mist coat can help on new plaster.
Why are doors and windows not subtracted exactly?
The calculator takes 1.6 square metres off for each door and 1.4 for each window, which are typical. Skirting boards and frames need painting too, so this is an allowance, not a precise measurement.