Paint Calculator
Works out paint from the area you are covering. Enter the surface area and the number of coats, and it gives the litres, the US gallons and the tins to buy.
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
The formula
litres = area ÷ coverage per litre × coats
Coverage is the whole calculation, and it is the figure tins are most optimistic about. The label quotes a smooth, sealed, previously painted surface; bare plaster, textured render and a strong colour change all take noticeably more.
What to watch out for
Coverage is where estimates go wrong, and it goes wrong in one direction:
- The tin is quoting its best case. 12–14 m²/L assumes a smooth, sealed, previously painted surface in a similar colour.
- Bare plaster drinks the first coat. New plaster needs a mist coat — paint thinned about 70:30 with water — before anything else, and that coat is largely absorbed.
- Texture multiplies the area. Woodchip, heavy relief paper and rough render can take half as much again as the flat area suggests.
- Dark to light needs three coats. No amount of hoping makes two work over a strong colour.
Buy it all at once. Paint is mixed in batches and two tins of the same colour code can differ enough to show as a band on a long wall.
Frequently Asked Questions
How much paint do I need per square metre?
About 0.09 litres per square metre per coat at 11 m²/L — so roughly 0.18 L/m² for two coats. A 40 m² area takes around 7.3 litres.
How many square feet does a gallon of paint cover?
About 450 square feet per coat at typical coverage, though many US manufacturers quote 350–400 to be safe. For two coats, budget a gallon per 200 square feet.
How many coats of paint do I need?
Two for most jobs. One is enough over the same colour in sound condition. Three when going light over dark, or over bare plaster that has had a mist coat.