A quality grade is a composite evaluation of factors that affect palatability of meat (tenderness, juiciness, and flavor). These factors include carcass maturity, firmness, texture, and color of lean, and the amount and distribution of marbling within the lean. Beef carcass quality grading is based on (1) degree of marbling and (2) degree of maturity.
Marbling (intramuscular fat) is the intermingling or dispersion of fat within the lean. Graders evaluate the amount and distribution of marbling in the ribeye muscle at the cut surface after the carcass has been ribbed between the 12th and 13th ribs. Degree of marbling is the primary determination of quality grade.
Each degree of marbling is divided into 100 subunits. In general, however, marbling scores are discussed in tenths within each degree of marbling (e.g.,Slight 90, Small 00, Small 10).
| Grade | Marbling Score |
| Prime + | Abundant 00-100 |
| Prime ° | Moderately Abundant 00-100 |
| Prime – | Slightly Abundant 00-100 |
| Choice + | Moderate 00-100 |
| Choice ° | Modest 00-100 |
| Choice – | Small 00-100 |
| Select + | Slight 50-100 |
| Select – | Slight 00-49 |
| Standard + | Traces 34-100 |
| Standard ° | Practically Devoid 67-100 to Traces 00-33 |
| Standard – | Practically Devoid 00-66 |
In addition to marbling, there are other ways to evaluate muscle for quality. Firmness of muscle is desirable, as is proper color and texture. Desirable ribeyes will exhibit an adequate amount of finely dispersed marbling in a firm, fine textured, bright, cherry-red colored lean. As an animal matures, the characteristics of muscle change, and muscle color becomes darker and muscle texture becomes coarser.
