You should know before painting the house

Specifications, coating norms of each type.
Each paint according to factory specifications 1kg of paint covers how many square meters of wall.
Calculate the area of the wall to be painted by yourself and ask the painter to recalculate that area, thereby comparing the norm to the amount of paint, also from the painter's spreadsheet, so that the painter can determine the full paint package. types.
If the painter exceeds the norm by 1.5 times, it must be reconsidered.