By definition, ground beef is fresh or frozen chopped meat from various parts of the cow, according to the Texas A&M Agrilife Extension Service. If the label denotes a particular cut, such as round or chuck, it can only come from that part of the animal. If it is simply labeled ground beef or hamburger, the meat and fat can come from multiple cuts.
Ground round is generally the leanest of the three cuts, at 90 percent lean and only 10 percent fat, reports the University of Wisconsin-Madison. Ground chuck typically weighs in at 85 percent lean. Unless otherwise specified, most meat labeled ground beef is 70 percent lean. Check the label, though. Ground beef may contain as much as 95 percent lean meat, according to the U.S. Department of Agriculture’s Nutrient Database.