It depends on the size of the room and a few other factors. A rule of thumb that I usually go by is that you’ll need approximately a gallon of paint per 400 square feet.
However, remember that that’s really just a very rough guideline. There are lots of different factors that come into play. For example, how many coats do you need? Are you mixing multiple colors? What kind of finish do you want, textured or smooth?
These will all affect the amount of paint you need. Use a paint calculator to get a more precise number and then add 10% for a little leeway. You could also just hire a painting company like Image Line Painting and let them calculate it for you.
