According to the high-quality ground beef purveyor Schweid & Sons, the most common ground beef choice among burger chefs is 80 percent lean, 20 percent fat. Law prohibits the sale of any ground beef with a fat content above 30 percent. While some consumers may scoff at the notion of buying beef that’s 20 percent fat, Schweid & Sons notes that the fat that surrounds the meat gives it a rich, juicy flavor. In fact, Schweid & Sons says that beef with lower-fat compositions, such as 85 percent lean and 15 percent fat, tends to dry out fast, which can adversely affect the flavor of the burger.