How Much Paint Do I Need?
The general rule is one gallon for every 350 square feet of surface area. All you have to do is measure walls roughly, then go to Sherwin-Williams.com and type the dimensions into the easy online paint calculator. This tool will also ask for measurements of windows, doors, and trim so it can come up with a more precise total. Whatever the number, buy an extra quart for touch-ups. A new batch mixed later might not match.