Paint Calculator
Litres of paint and primer for a room after deducting doors and windows, with pack sizes and cost.
About Paint Calculator
This paint calculator estimates how many litres of paint and primer you need for a room. Enter the room length, width and height, subtract the doors and windows, and set the number of coats and the coverage printed on the paint can.
It suggests pack sizes and gives a cost estimate, so you can buy the right amount of emulsion or enamel for your home. You can include or skip the ceiling and use it for one wall or a whole house. It is free, works in square feet or square metres and runs in your browser without sign-up.
How to use Paint Calculator
- Enter the room length, width and height.
- Add the number and size of doors and windows to deduct.
- Set coats and coverage from the paint can label.
- Read litres of paint and primer and suggested pack sizes.
Frequently asked questions
How much area does 1 litre of paint cover?
Interior emulsions cover roughly 100–160 sq ft per litre per coat on a smooth primed wall. Rough or new plaster absorbs more. Always check the manufacturer’s label.
How many coats do I need?
Two coats of finish paint over one coat of primer is standard for new walls. Repainting the same colour may need only one coat.
Should the ceiling be included?
Tick “Include ceiling” if the ceiling gets the same paint. Many people use a cheaper ceiling white instead.
How do I calculate paint for a room?
Find the wall area (perimeter × height), subtract doors and windows, multiply by the number of coats and divide by the coverage per litre.
How much paint do I need for a 10 × 12 room?
With 10 ft walls, the wall area is about 440 sq ft; two coats of emulsion usually need about 8–10 litres, depending on coverage.
Do I need primer before painting?
Yes for new plaster, bare surfaces or a big colour change; the calculator estimates primer separately.
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