--- title: "How many coats of paint do I need? | BuildBatch" description: "At an example 10 m² per litre, a 4 m × 3 m room's walls need 3.385 L for one coat, 6.77 L for two and 10.154 L for three. The tin decides the coats." url: https://buildbatch.co.uk/guides/how-many-coats-of-paint-do-i-need/ --- [Guides](https://buildbatch.co.uk/guides/) # How many coats of paint do I need? 5 min read · Updated 2 October 2026 ![A paint tin and a pack of flooring, each with a label tag.](https://buildbatch.co.uk/app/img/step-choose.svg) The tin says, for that paint and that surface, and BuildBatch works with the number you enter. It starts at 2 coats, a labelled example. For the walls of a 4 m × 3 m room 2.4 m high, at an example 10 m² per litre with 10% extra, one coat needs 3.385 L, two coats 6.77 L and three coats 10.154 L: 2, 3 and 5 of the example 2.5 L tins. ## The sum Paint needed in litres = area × coats ÷ coverage × (1 + extra ÷ 100). Coats is a whole number from 1 to 10, and the litres go up in step with it. The sum is worked through in [how much paint do I need?](https://buildbatch.co.uk/guides/how-much-paint-do-i-need/) ## One room at 1, 2 and 3 coats A room 4 m × 3 m and 2.4 m high, with one internal door 762 mm × 1981 mm and one window 1.2 m × 1.1 m taken off. The walls come to 30.77 m² (33.6 m² less 2.83 m²) and the ceiling to 12 m². The coverage, the extra and the tin are the planner’s generic examples, not the figures of any paint: 10 m² per litre, 10% extra and 2.5 L tins. Only the coats change. | Coats | Walls need | Walls: tins | Ceiling needs | Ceiling: tins | | --- | --- | --- | --- | --- | | 1 | 3.385 L | 2 × 2.5 L (5 L) | 1.32 L | 1 × 2.5 L (2.5 L) | | 2 | 6.77 L | 3 × 2.5 L (7.5 L) | 2.64 L | 2 × 2.5 L (5 L) | | 3 | 10.154 L | 5 × 2.5 L (12.5 L) | 3.96 L | 2 × 2.5 L (5 L) | - **The litres rise in step.** Each coat adds about 3.385 L to the walls and 1.32 L to the ceiling. - **The tins rise in whole tins.** A third coat on the walls takes 2 more tins, from 3 to 5, and leaves about 2.346 L. A third coat on the ceiling takes none: the same 2 tins do two coats or three, leaving about 2.36 L after two and about 1.04 L after three. ## What BuildBatch starts with 2 coats, 10 m² per litre, 10% extra and a 2.5 L tin. Each paint line says “2 coats (generic example)” until you change it. They are examples so that you can get an answer before you have a tin: they are not manufacturer data and not a recommendation. ## The tin decides The tin’s own instructions decide the number of coats for that paint and that surface. BuildBatch does not know your paint, so it asks for what the tin says: how many m² a litre covers in one coat, how many coats it says, and the tin sizes. Enter the coats from the tin, and the litres and tins follow. The planner’s own lines on the subject are short: - **A sound, previously painted surface.** Primer or sealer is marked Not needed, with this line: “Check the paint’s instructions for a strong colour change or a glossy surface.” - **New or bare plaster.** A mist coat or primer-sealer is marked Check first, with the warning that two top coats straight onto bare plaster may not cover and that the paint’s instructions for bare plaster decide. See [painting new plaster: mist coat, primer and how many coats](https://buildbatch.co.uk/guides/mist-coat-and-primer-for-new-plaster/). - **A strong colour change.** [Paint coverage explained](https://buildbatch.co.uk/guides/paint-coverage-explained/) says it may need an extra coat rather than more paint per coat. ## Coats and coverage together The tin gives two figures that move the answer, the coats and the coverage. The walls of the same room, in litres, with all three coverages as examples: | Coverage | 1 coat | 2 coats | 3 coats | | --- | --- | --- | --- | | 10 m² per litre | 3.385 L | 6.77 L | 10.154 L | | 12 m² per litre | 2.821 L | 5.641 L | 8.462 L | | 14 m² per litre | 2.418 L | 4.835 L | 7.253 L | [How far does a tin of paint go?](https://buildbatch.co.uk/guides/how-far-does-a-tin-of-paint-go/) goes through the coverage on its own. ## Do it with BuildBatch Open the [room refresh planner with paint chosen](https://buildbatch.co.uk/room-refresh/?work=paint), type the room, add the doors and windows, and enter the coats, the coverage and the tin sizes from your paint. It gives the litres and the tins for the walls and the ceiling, with what is left over. The [paint calculator](https://buildbatch.co.uk/paint-calculator/) does the same sum for walls and ceilings on one page. ## What this guide does not cover How many coats a particular paint, colour, surface or finish needs: the tin and the maker’s data sheet say. Primer, undercoat and mist coat figures, which come from their own tins. Woodwork. Exterior and masonry paint. Which tin size costs less, which is in [2.5 litre or 5 litre tin: which costs less?](https://buildbatch.co.uk/guides/paint-2-5-litre-or-5-litre-tin-which-costs-less/) ## Related guides - [How much paint do I need?](https://buildbatch.co.uk/guides/how-much-paint-do-i-need/) - [How far does a tin of paint go? 1, 2.5, 5 and 10 litres](https://buildbatch.co.uk/guides/how-far-does-a-tin-of-paint-go/) - [Painting new plaster: mist coat, primer and how many coats](https://buildbatch.co.uk/guides/mist-coat-and-primer-for-new-plaster/) ## Questions **How many coats of paint do I need for walls?** The tin says, for that paint and that surface. BuildBatch starts at 2 coats as a labelled example, and you replace it with the tin's number. At an example 10 m² per litre, the walls of a 4 m × 3 m room 2.4 m high need 6.77 L for two coats. **How much more paint does a third coat need?** About half as much again as two coats. The walls of the example room go from 6.77 L to 10.154 L, which is 3 tins of 2.5 L to 5. Its ceiling goes from 2.64 L to 3.96 L, which is 2 tins both times. **How much paint for one coat?** The same room needs 3.385 L for the walls and 1.32 L for the ceiling at an example 10 m² per litre with 10% extra: 2 tins of 2.5 L for the walls and 1 for the ceiling. Whether one coat is enough is for the tin to say. **Does a mist coat count as a coat?** A primer-sealer is a separate product with its own line. A mist coat of the same emulsion can be counted by raising the wall paint's coats by one, as a planning figure: for the example walls, from 2 coats to 3, which is 6.77 L to 10.154 L. The paint's instructions for bare plaster decide. **Want the sum done for you?** It works from your own measurements and product figures, and shows its working. [Work out the paint for a room](https://buildbatch.co.uk/room-refresh/?work=paint) A worked example: [How much paint for a 3 x 4 m bedroom?](https://buildbatch.co.uk/examples/painting-a-3-by-4-m-bedroom/) [All calculators](https://buildbatch.co.uk/calculators/) · [Example lists and tables by room size](https://buildbatch.co.uk/examples/)