Paint Calculator
Work out how much paint a room needs: walls and ceiling less doors and windows, coats and the coverage on your tin, plus wastage — and the tins to buy.
Paint
- Area to paint
- 43.4 m² (467 sq ft)
- Coats
- 2
- Walls 48.3 m² (520 sq ft), less 4.9 m² (53 sq ft) of doors and windows.
- Litres = area × coats ÷ coverage per litre per coat, plus 10% for wastage and touch-ups. The tins are the mix that leaves the least over, then the fewest tins.
- Coverage depends on the paint and the wall: rough, porous or new plaster takes more. Primer and putty are separate.
Walls and paint
How is this calculated?
Litres = area to paint × coats ÷ coverage per litre per coat × (1 + wastage). Area = 2 × (length + width) × height − doors − windows (+ ceiling).Runs in your browser — nothing you enter leaves this device.
About this tool
What it does
Paint Calculator works out how many litres of paint a room or a wall needs and which tins to buy. Enter the room’s length, width and height (in feet or metres) and it finds the wall area — the perimeter times the height — takes off your doors and windows, and adds the ceiling if you are painting it; or type an area directly. Then the number of coats (two is usual for a new colour) and the coverage of your paint: how many square feet or square metres one litre covers in one coat, which is printed on the tin or the maker’s product sheet and differs a lot between paints. Ten per cent is added for wastage, touch-ups and the paint left in the tray, and you can change it. The answer is the litres needed, and the mix of tin sizes that leaves the least paint over — with the fewest tins when two mixes are equal — using the sizes your paint is sold in, such as 20, 10, 4 and 1 litre, or 18, 9, 3.6 and 0.9.
How to use it
- Enter the room, or the area to paint.
- Choose the coats and enter the coverage from the tin.
- Check the wastage and the tin sizes.
- Read the litres and the tins to buy.
Limits and your data
- Coverage on a tin assumes a smooth, primed wall; new plaster, rough or porous walls and dark-to-light colour changes take more.
- Primer, putty and texture are separate products with their own coverage; work them out separately.
- Doors are taken as 3 × 7 ft (0.9 × 2.1 m) and windows as 4 × 4 ft (1.2 × 1.2 m).
- Everything is worked out in your browser. Nothing is sent anywhere.
Questions
How much paint do I need for a 10 × 12 room?
With a 10 ft ceiling, the walls are 440 sq ft; less a door and two windows, about 390 sq ft. Two coats at 120 sq ft a litre with 10% extra is about 7.1 litres.
How many coats do I need?
Two, for a new colour or new wall; one can do for a fresh coat of the same colour on a sound wall.
Where do I find the coverage?
On the tin, the shade card or the maker’s website, often per litre per coat or for two coats — divide by two if it is for two.
Why does it suggest several small tins?
It buys the least paint beyond what is needed. Larger tins are often cheaper a litre; choose a bigger one if the price is better.