Beef Carcasses are graded by the Livestock and Seed Division of the USDA Agricultural Marketing Service. Grading is done on a fee basis, such that processors cover the cost of running the USDA Beef Grading system. There are generally two grades applied to a qualifying carcass: Quality Grade and Yield Grade.
Quality Grade is a measurement used to predict the palatability of the lean. This is based primarily on marbling, although several determinants of animal age also affect the Quality Grade. Maturity scores are given from A to E, with only A maturity animals being eligible for the Prime Quality Grade designation. Steers and heifers are eligible for Prime, Choice, Select, Standard, Commercial, Utility, Cutter, and Canner. Except for Prime, the same designations are applied to cow carcasses. Bullock carcasses are eligible for Prime, Choice, Select, Standard, and Utility. Dark meat with a sticky consistency or meat with speckled blood splatter disqualify an animal for these grades.
The Quality Grade designation is based on the marbling in the ribeye (longissimus dorsi) between the 12th and 13th ribs.
Slightly Abundant (Prime)
Yield Grade is the indicated yield of closely trimmed (1/2 inch fat or less), boneless retail cuts expected to be derived from the major wholesale cuts (round, sirloin, short loin, rib, and square-cut chuck) of a carcass. Yield Grade is indicated on a scale of 1 to 5, with Yield Grade 1 representing the highest degree of cutability.
Yield Grade equals 2.50 + (2.50 x adjusted fat thickness, inches) + (0.20 x percent kidney, pelvic, and heart fat) + (0.0038 x hot carcass weight, pounds) - (0.32 x ribeye area, square inches)