4 coats if cutting with 1000-1200 to start, 3 coats if starting with 1500 or finer is usually what I do. How it comes out and what you want to end up with determines how much material you need to correct problems like urethane wave, orange peel, and trash. While you are spraying, look at what you have between each coat. If it looks like you want after 3, with only minor orange peel and trash, really no need to spray more. If it has lots of issues, another coat gives you a sacrificial coat to sand away. The first coat is the most important.. It will determine what the finished product will look like. My guess is you will have enough clear for 3 coats on what you are spraying, but 4 or more you may run short with a gallon.