One of the first considerations when it comes to interior house paint is the base. There are two schools of thought, each with their pros and cons. Some brands commonly sold to contractors for commercial projects are oil-based, meaning the chosen pigment is mixed with an oil derivative called alkyd. Oil-based paint provides thorough coverage, and the finished coat resists moisture well. However, oil-based paint releases a high level of volatile organic compounds (VOCs) as it dries, and it can only be removed from floors, brushes, and clothing with strong chemical paint thinners. In fact, many states have actually banned the use of oil-based paints because of their VOC levels and hazardous ingredients.
The Ceiling. For ceilings, flat is recommended, except semigloss or satin should be used in bathrooms with showers/tubs. Some customers opt to go with a different finish for ceilings in general, to create a specific design look, i.e. high gloss ceilings on dining room tray ceiling to make a statement, or eggshell ceilings throughout to look modern and make a statement.
For trim and doors, start with 1 gallon (3.8 L) of trim paint for every 600 sq feet of floor space. Purchase more at the store if/when needed. Trim is something that is difficult to calculate exactly, and it is more time-efficient to simply start with less than you need, and go buy more after you have used up the first round of paint and determined how much you will need to finish by seeing how much you have painted so far, compared to the gallons used.