Prime Rib Cooking Time per Pound (USDA Rib Roast Times)
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The USDA's beef roasting table gives a bone-in rib roast of 4 to 6 lb about 23 to 25 minutes per pound at 325 °F. A boneless rolled rib roast needs 5 to 8 minutes more per pound. Cook it to at least 145 °F and let it rest at least 3 minutes.
Times by weight at 325 °F
| Roast | Bone-in (23–25 min/lb) | Boneless (28–33 min/lb) |
|---|---|---|
| 4 lb | 1 h 32 min to 1 h 40 min | 1 h 52 min to 2 h 12 min |
| 5 lb | 1 h 55 min to 2 h 05 min | 2 h 20 min to 2 h 45 min |
| 6 lb | 2 h 18 min to 2 h 30 min | 2 h 48 min to 3 h 18 min |
The math: weight × minutes per pound. For boneless, add the USDA's 5 to 8 extra minutes to each end: 23 + 5 = 28 and 25 + 8 = 33 minutes per pound.
Done temperature
The USDA's safe minimum for beef roasts is 145 °F, measured with a food thermometer, followed by a rest of at least 3 minutes. The USDA figure is a safety minimum.
Planning the meal
Count back from dinnertime: rest time, then the roasting time from the table, gives the time the roast goes into the oven. Example: a 5 lb bone-in roast for a 6:00 PM dinner, planned with the longer 2 h 05 min and the USDA's minimum 3-minute rest, goes in at about 3:52 PM (6:00 − 0:03 rest − 2:05). Allow more time if you want a longer rest.
Other beef roasts in the same USDA table
| Cut | Size | Oven | Time |
|---|---|---|---|
| Round or rump roast | 2½ to 4 lb | 325 °F | 30 to 35 min/lb |
| Whole tenderloin | 4 to 6 lb | 425 °F | 45 to 60 min total |
| Chuck roast or brisket (braised) | 3 to 4 lb | 325 °F | 1½ to 2½ hours |
All are cooked to at least 145 °F with a 3-minute rest.
Thaw the roast safely
FSIS lists refrigerator, cold water and microwave thawing for beef; do not thaw it on the counter. A whole roast may need 2 days or longer in the refrigerator. Once thawed there, raw beef can remain refrigerated 3–5 days before cooking. For cold-water thawing, keep the package airtight and change the water every 30 minutes; FSIS estimates a 3–4 lb roast can take 2–3 hours. Cook beef immediately after microwave thawing.
When checking a large roast, FSIS says to use a food thermometer in several places. The internal temperature, followed by the required rest, determines safety; the minutes-per-pound estimate is only for planning.
Sources
- U.S. Department of Agriculture, Food Safety and Inspection Service, Beef From Farm to Table ("Approximate Beef Cooking Times").