It usually takes about two gallons of paint to cover a room. Paint comes in three different finishes; flat, semi-gloss, and high-gloss, and can range anywhere from $30-$60. Flat finishes are the least shiny of the three finishes and are best suited for areas such as long walls where you’re trying to hide imperfections. You also want to use flat paint in areas of the house where you want the paint to stand out. Semi-gloss finishes are a bit shiny but can also be easily cleaned, and are best used for painting the trim. A high-gloss finish is stain-resistant and easy to clean. Glossy paints are best used for like high traffic spots, such as the hallways. For your paint job, you may also need a primer, especially if your old layer is darker than your new color. Primer typically costs anywhere from $12-$25, and you will need at least 1-2 cans of primer to cover one room.