Paint Calculator
Litres first, then round up to a pack size. Buying a second tin later rarely matches the first.
Two coats is not marketing
One coat over new plaster shows every patch. Three is normal going dark to light.
Primer is separate
New plaster needs a sealer coat, and it is not included in paint coverage.
How much does 1 litre cover?
About 110–130 sqft per coat on smooth emulsion.
20L or 4L?
20L is cheaper per litre but spoils once opened.