The prime rib roasting chart was created by cooking meat of different sizes at the same temperature to determine the cooking time needed for the meat to gain the internal temperature of 120 degrees Fahrenheit and be considered rare. Other charts are available for medium rare, medium, medium well, and well done meats. All charts contain the estimated cooking time and temperature needed for prime ribs ranging from 4 to 19 pounds to achieve the desired cooked state.
To cook prime rib, start with a room temperature cut of meat and 2 tablespoons of butter. Dry the prime rib with paper towels and cover the cut ends with butter. Put the ribs in a roasting pan; the fat side should face up. Place in the oven and sear for 15 minutes at 450 degrees Fahrenheit, and then turn the oven's temperature to 325 degrees Fahrenheit. Use the fat melting into the pan, and baste the meat every half hour.
Use the prime rib roasting chart to determine the cooking time appropriate for the size of the meat and the desired level of cooking. Approximately 45 minutes before the time is up, use a meat thermometer to check the internal temperature. Rare meat is cooked at 120 to 125 degrees Fahrenheit, while medium rare is complete at 130 to 135 degrees Fahrenheit. Medium is done at 140 to 145 degrees Fahrenheit, and medium well meats are fully cooked at 150 to 155 degrees. Meat is considered well done at temperatures 160 degrees Fahrenheit or greater.