Paint Calculator is super feature that gives us undestanding amount of paint we require for the painting project plus in nearest future we can calculate labour cost for the painting protect. of course professional painters knows in and out quanaties of ceiling, wall and wood work paint. Usally for 3 bedroom unit/house takes 20L of ceiling paint in most cases its flat (bathroom ceilings best to use mould proof or simple low sheen paint, 30 litres for walls usually its low sheen, and 4-6 Litres for wood work. Coverage in most cases around 1L per 10 Square meters Again its for previously painted surfaces only. For new plaster board its around 8 squares per 1 L, and new render is 5 square meters per litre.