--- title: "Paint Calculator for Walls & Ceilings | Little Courtyard" description: "Work out how much paint a room needs: walls less doors and windows, coats, ceiling and primer, in litres or US gallons, with the tins to buy." url: https://littlecourtyard.homes/ --- Walls, ceiling & primer # Paint calculator How much paint a room needs: the walls from the room's size or one wall at a time, less doors and windows, times the coats, at the coverage printed on your tin. In litres or US gallons, with the tins to buy. ## How to use the paint calculator Choose **Whole room** and enter the floor's length and width and the wall height; the calculator walks round all four walls. For a feature wall, a stairwell or an odd-shaped room, choose **Wall by wall** and add each wall's width and height (a sloping wall can be entered at its average height). Count the **doors and windows** and give a typical size; the example uses a common UK internal door (762 × 1981 mm) and a US one in imperial (30 × 80 in). Use the extra box for anything else that stays unpainted, such as a tiled splashback. **Coverage** is the area one litre (or one US gallon) covers in one coat. It is printed on the tin and differs a lot between products, so replace the typical figure with yours. **Extra** adds a margin for paint left in rollers and trays and for touch-ups. The **ceiling** and the **primer** are worked out on their own lines because they are usually different products. Tick the tin sizes your shop sells. The calculator shows the mix that leaves the least paint over and, when it uses fewer tins, the fewest-tins choice as well. ### Worked example A 4 × 3.5 m room with 2.5 m walls has 2 × (4 + 3.5) × 2.5 = 37.5 m² of wall. Taking off a door (1.51 m²) and a 1.2 × 1.2 m window (1.44 m²) leaves 34.55 m². Two coats at 10 m²/L is 6.91 litres, or 7.6 litres with 10% extra: a 5 L tin and three 1 L tins, or a single 10 L tin. ## Coverage printed by paint makers Two published figures show how far apart labels can be. Sherwin-Williams puts a gallon of paint at about 350–400 ft² (8.6–9.8 m² per litre) and a gallon of primer at about 200–300 ft² (4.9–7.4 m² per litre). Dulux lists its Dulux Matt emulsion at "up to 14m2/litre" with two coats. An "up to" figure is the best case; textured, porous or patched walls take more. The defaults are 350 ft²/gal in imperial, the low end of the Sherwin-Williams figure, and 10 m²/L in metric, between that figure and the "up to" on UK emulsion tins. Primer starts at 250 ft²/gal (6 m²/L), the middle of the Sherwin-Williams primer range. ## Sources - Sherwin-Williams, [Paint Calculator and FAQ](https://www.sherwin-williams.com/en-us/color/color-tools/paint-calculator): about 350–400 ft² per gallon of paint and 200–300 ft² per gallon of primer; amounts vary with the application method and the surface. - Dulux UK, [Dulux Matt product page](https://www.dulux.co.uk/en/products/dulux-matt): coverage "up to 14m2/litre", two coats, tin sizes. ## More room calculators From the walls to the floor, with the same units throughout. - [Wallpaper roll calculator](https://littlecourtyard.homes/wallpaper-calculator/): Strips per roll and rolls to buy, with the pattern repeat, straight or half-drop match, for Euro rolls, US double rolls or your own. - [Tile calculator](https://littlecourtyard.homes/tile-calculator/): Tiles and boxes for a floor or wall, with the joint, the layout (straight, brick, diagonal, herringbone) and a waste allowance. - [Grout calculator](https://littlecourtyard.homes/grout-calculator/): Kilograms or pounds of grout and the bags to buy, from the tile size, joint width and depth, by the grout makers' own formula. - [Room area & floor plan sketch](https://littlecourtyard.homes/floor-plan-area-calculator/): Draw rooms on a grid or type their sizes, see each area and perimeter in m² and ft², and save the plan as SVG or PNG. ## Recommended Two free services for the online side of decorating. Temporary email · no sign-up ### CleanTempMail Colour charts, sample pots, wallpaper swatches and DIY-store discount codes often arrive only after you hand over an email address. CleanTempMail opens a free disposable inbox at once, with no sign-up, a random or custom address on hundreds of domains, and messages deleted automatically after 3 days. [Get a temporary inbox](https://cleantempmail.com/) Disposable cloud browser · domain lookups ### WebTraceCheck Found designer tiles or trade paint far cheaper on a shop you have never heard of? WebTraceCheck's free DNS and domain lookup shows the details behind the site's domain, and its disposable cloud browser opens unfamiliar links on an isolated desktop that is deleted after each session. [Look into a shop first](https://webtracecheck.com/) ## Questions **How much paint do I need for a 12 × 12 ft room?** With 8 ft walls that is 384 ft² of wall. Take off a 30 × 80 in door and a 4 × 4 ft window and about 351 ft² is left. Two coats at 350 ft² per gallon need just over 2 gallons, so 2 gallons and a quart, before any extra. A metric room of 3.6 × 3.6 m with 2.4 m walls works out at about 6.3 litres for two coats at 10 m²/L. **Should I take doors and windows off the wall area?** Yes for anything large, like doors, patio doors and big windows. Small windows make little difference, and leaving them in simply gives you a little spare paint. Remember to add the door itself if you are painting it, usually with a different paint. **How many coats of paint do walls need?** Follow the tin. Many wall paints ask for two coats; Dulux, for example, lists two coats for Dulux Matt. A big change of colour, a dark colour over a light one or a fresh surface can need a third coat or a primer first. **What does "up to 14 m² per litre" on the tin mean?** It is the best case: what one litre covers in one coat on a smooth, sound surface. Rough, porous, patched or textured walls take more paint, so real coverage is often lower. That is why the calculator starts below the labels and adds an extra allowance you can change. **How do I work out paint for the ceiling?** The ceiling area is the room's length times its width. Tick "Paint the ceiling too" and the calculator adds a separate line for it, with its own coats and coverage, because ceiling paint is usually a different product from the walls.