Prime Rib Cooking Chart:

Click on photo for more information

The chart below is only a guide. You must rely on an accurate Meat Thermometer and start taking temperatures about 45 minutes before the end of the estimated roast time.

Reminder: Instant read thermometers are not meant to be left in the roast during the cooking process.

What constitutes rare and medium-rare cooked meat?To satisfy government home economists, the Beef Council says rare beef means an internal temperature of 140 degrees F. Well, that is ok if you like well-done and dry meat. If you like moist, rosy meat (like I do), rare begins at 120 degrees F. and starts to become medium rare at 125 to 130 degrees F. To cook your meat properly, you must purchase and use a good instant-read digital meat thermometer. This is the type of cooking and meat thermometer that I prefer and use in my cooking.  I get many readers asking what cooking/meat thermometer that I prefer and use in my cooking and baking. I, personally, use the Thermapen Thermometer shown in the photo on the right. Originally designed for professional users, the Super-Fast Thermapen Thermometer is used by chefs all over the world. To learn more about this excellent thermometer and to also purchase one (if you desire), just click on the underlined: Thermapen Thermometer. Also learn How To Test and Calibrate a Cooking or Meat Thermometer.

	Approximate Weight	Oven Temperature	Total EstimatedTime Only	Meat Thermometer Reading (Rare)
2 ribs	4 to 5 pounds	450 deg/325 deg F	60 to 70 minutes	120 degrees F
3 ribs	7 to 8.5 pounds	450 deg/325 deg F	1 1/2 to 1 3/4 hours	120 degrees F
4 ribs	9 to 10.5 pounds	450 deg/325 deg F	1 3/4 to 2 1/4 hours	120 degrees F
5 ribs	11 to 13.5 pounds	450 deg/325 deg F	2 1/4 to 2 3/4 hours	120 degrees F
6 ribs	14 to 16 pounds	450 deg/325 deg F	3 to 3 1/4 hours	120 degrees F
7 ribs	16 to 18.5 pounds	450 deg/325 deg F	3 1/4 to 4 hours	120 degrees F

How To Check Oven Temperature – Oven temperatures are not always correct. In fact, they can often be off by 25°F to 50°F. The will seriously affect the baking time of your prime rib (standing rib roast). To check the temperature of your oven, place an oven thermometer on the center rack and heat the oven for 15 minutes at 350°F. If, after 15 minutes, the oven temperature reads higher or lower than your oven setting, adjust your oven setting for your prime rib baking and for all your future baking.

Beef Roast Cooking Temperatures
Rare	120 to 125 degrees F	center is bright red, pinkish toward the exterior portion
Medium Rare	130 to 135 degrees F	center is very pink, slightly brown toward the exterior portion
Medium	140 to 145 degrees F	center is light pink, outer portion is brown
Medium Well	150 to 155 degrees F	not pink
Well Done	160 degrees F and above	steak is uniformly brown throughout

High Altitude Baking: 

Above 2,500 feet, the atmosphere becomes much drier. The air has less oxygen and atmospheric pressure, so cooking takes longer. Use the sea-level time and temperature guidelines when oven-roasting beef, as oven temperatures are not affected by altitude changes. 

Allow additional cooking time for your prime rib roast at high altitude. I can not give you the exact cooking time.  A food thermometer is the only way to measure whether your roast has reached a safe internal temperature. In a high altitude environment, it is easy to overcook meat.