How much paint do I need?
Measure the wall, take away windows and doors, multiply by the coats and divide by what one can covers. Here is the rule, a worked example and a free calculator that does it for you.
How much paint do I need for one wall?
Multiply the wall's width by its height, subtract each window and door, then multiply by the number of coats. Divide by the coverage on the can, which is often about 10 m² per litre or 375 ft² per US gallon, and round up to the next whole can size.
gallons = (wall area − openings) × coats ÷ 375 ft²
Worked example
- Wall 4.2 m wide × 2.7 m high = 11.34 m² (14 ft × 9 ft = 126 ft²).
- Take away a door, 0.9 m × 2.1 m = 1.89 m² (3 ft × 7 ft = 21 ft²). That leaves 9.45 m² (105 ft²).
- Two coats: 18.9 m² (210 ft²).
- 18.9 ÷ 10 = 1.89, so buy 2 litres. In gallons, 210 ÷ 375 = 0.56, so 1 gallon.
How many coats of paint do I need?
Two coats is normal for a repaint, because the second coat evens out patchy areas and gives the colour its true depth. Use three coats when a light colour goes over a dark one, or on fresh plaster after a primer. A single coat only works when the new colour is very close to the old one.
Why does my can say a different coverage?
Coverage depends on the paint and the wall. Most interior paints state roughly 350 to 400 ft² per gallon, or about 10 to 12 m² per litre, on a smooth primed wall. Rough, porous or textured walls drink more paint. Roomveil uses the lower figure so you are less likely to run short.
See the colour before you buy
Roomveil lets you tap a colour and see it on a photo of your own wall, with the shadows and light from your room kept. It then works out the litres or gallons for you, in any unit you measured in.
These are common rules of thumb and code minimums, given for planning. Always check the product label, the maker's instructions and your local building code before you buy or build.