Paint calculator: litres, tins and cost for your room
Enter your wall sizes to see how much paint to buy, which tins to pick and what it might cost, including a feature wall and the ceiling.
Your paint (estimate)
Main colour walls
- Area to paint
- 33.0 m²
- Coats
- 2
- Paint needed
- 6.05 litres
- Tins to buy
- 1 x 5 L + 2 x 1 L (7 L)
- Estimated cost
- £44.40
Estimated total£44.40
Prices are indicative for October 2026 [estimate], per litre for 5 and 10 litre tins, 10% more for 2.5 litre and 20% more for 1 litre tins. Check your shop's price before buying.
How this calculator works
For each wall we multiply width by height. A UK door leaf is 762 x 1981 mm, about 1.5 m², and we deduct 1.6 m² per door to allow for the frame. Windows count as 1.44 m² each. These come off the main-colour walls only, and a feature wall is painted in full.
The area for each colour is divided by coverage, multiplied by the number of coats, then increased by 10% for waste and rounding up to the next 0.01 litre. New plaster adds one mist coat, and a dark colour over a light one is set to at least three coats, which is trade practice.
Manufacturers quote best-case coverage: Dulux Matt is up to 14 m² per litre, Dulux Easycare 13, Dulux Trade Vinyl Matt up to 17, Crown Matt 14, Wickes 13 and GoodHome 10. Our default of 12 is about 85% of the 14 m² label, so it allows for rough walls and normal application. Use the advanced options to pick a preset or enter your own figure.
A few buying tips: buy all the paint for one colour together so the batches match, round up rather than down if your walls are porous or textured, and keep a little left over for touch-ups. Results are estimates, because real coverage depends on the surface, the paint and how you apply it.
Fresh plaster is thirsty. Follow the Dulux new plaster guide, which describes a 10 to 1 mist coat. Then we choose the cheapest tins from 10, 5, 2.5 and 1 litre sizes that cover your total. Painting the shed or fence as well? Our lawn watering calculator has your garden covered too.
Frequently asked questions
How many litres of paint do I need per square metre?
At our default coverage of 12 square metres per litre, one coat needs about 0.083 litres per square metre. Two coats need about 0.17 litres, and our 10% allowance for waste lifts that to roughly 0.18 litres. A 4 m by 2.4 m wall with a door needs about 1.5 litres of emulsion for two coats.
Do I need two coats of paint?
Usually, yes. Two coats give an even colour and a proper finish, so the calculator defaults to two. Painting a dark colour over a light one often takes three, so tick the dark-over-light option. Trade painters commonly use three coats for that job.
What is a mist coat and when do I need one?
A mist coat is watered-down emulsion, about ten parts paint to one part water, used as the first coat on new plaster so it soaks in rather than sealing the surface. Tick the new plaster option and the calculator adds one extra coat at the same coverage. Dulux explains the method in its new plaster guide.
How do I plan a feature wall in a different colour?
Tick "Feature wall" on one wall. The calculator then works out that wall separately, so you buy the right tin for the accent colour and for the main colour. Doors and windows are deducted from the main-colour walls only, so the feature wall figure may be slightly generous if it has a window.
What tin sizes does the calculator use?
It picks from 10 litre, 5 litre, 2.5 litre and 1 litre tins. It chooses the combination with the lowest total cost that still covers the paint you need. If two combinations cost the same, it prefers fewer tins. Smaller tins cost more per litre, so one large tin is often cheaper than several small ones.
Does the estimate include the ceiling?
Only if you switch the ceiling option on and enter its length and width. The ceiling is then worked out as its own colour group, because it is usually white or brilliant white. It uses the same coats and coverage as your walls.