Ground hamburger: Ground from the least wanted cuts of meat.. The butcher reserves trimmings from other meat cuts to grind into hamburger and ground beef. This means in theory there could be pieces of sirloin, chuck, ribs, or even filet mignon in that package of hamburger. According to USDA standards, hamburger may have fat added, but cannot contain more than 30% fat by weight. As a general rule, it is not really sold in supermarkets.
Ground beef: Basically the same as ground hamburger but it cannot have added fat. It cannot contain more than 30% fat by weight.
Ground chuck : 80 to 85 percent lean / 15 to 20 percent fat
Ground round : 85 to 90 percent lean / 10 to 15 percent fat
Ground sirloin : 90 to 92 percent lean / 8 to 10 percent fat
One important note, when it states 80 percent lean, its actually not. Why? Because that 80 percent actually contains 10 percent of fat. So after a little bit of simple math, ground chuck actually contains 70 percent lean, and 30 percent fat.
EAT MORE BEEF!