Determined by the USDA, there are eight grades used to describe steak, with prime, choice, and select being the top ones. Beef is graded only if the producer pays for the service.

The first criterion for grading is the amount of marbling (fat) the steak has. As fat adds flavor and tenderness, more marbling means a higher-quality and thus a higher-grade cut.

The second one is the maturity of the slaughtered cow. As cows age, the increasing collagen and muscle exertion make their meat tougher, so younger cows result in a higher grade.

Note that beef grades are more about quality, taste, and to some degree, fat content. Per the USDA, protein, vitamin, and mineral contents of beef are similar across all grades.

The top grade is prime (the best and most pricey), which is followed by choice, and then select at the cheaper end. Their price differences vary depending on the store and the cut.

Prime beef is a hot commodity, and only about 3% of beef gets this grade. Prime rib nearly always falls within this category, as it has plenty of marbling and is around 8-13% fat.

Choice is the most common grade, with about half of all graded beef fitting this category. With moderate marbling and about 4-10% fat, ribeye and sirloin often fit into this grade.

The select grade often features cuts like chuck, shank, and brisket. With 2-4% fat, select beef isn't as juicy and tender as prime or choice beef, so it needs to be tenderized.