Prime rib cooking time calculator

How long do I cook a prime rib?

The USDA Food Safety and Inspection Service chart gives 23 to 25 minutes per pound at 325 °F for a 4- to 6-pound bone-in rib roast: a 5-pound roast takes about 1 hour 55 minutes to 2 hours 5 minutes. The Beef Checkoff chart, at 350 °F, gives 2¼ to 2½ hours for a 6- to 8-pound bone-in roast (2 to 4 ribs) cooked medium rare.

At what temperature do I take it out?

The Beef Checkoff says to remove a rib roast at 135 °F for medium rare or 145 °F for medium, then let it stand 15 to 20 minutes — the temperature keeps rising 5 to 15 °F. USDA FSIS recommends cooking beef roasts to at least 145 °F and resting them at least 3 minutes.

What about a boneless rib roast?

At 325 °F, FSIS says to add 5 to 8 minutes per pound to the bone-in time — 28 to 33 minutes per pound. At 350 °F, the Beef Checkoff gives 1¾ to 2 hours for a 4- to 6-pound small-end ribeye roast cooked medium rare, and 2 to 2¼ hours for the large end.

Is medium-rare prime rib safe?

USDA FSIS recommends 145 °F with a 3-minute rest for whole cuts of beef. A roast taken out at 135 °F keeps cooking as it rests; check it with a food thermometer in the thickest part, not touching bone or fat, if you want it to reach 145 °F.

Are the times exact?

No — they are for planning. FSIS bases its times on beef straight from the refrigerator at 40 °F, and ovens vary. Start checking the temperature before the shortest time.

When should I put the roast in if dinner is at 6:00?

Work backward: the cooking time, plus the 15 to 20 minutes the roast stands, plus a margin for checking. A 7-pound bone-in roast at 350 °F takes 2 h 15 min to 2 h 30 min for medium rare, so with a 20-minute stand it should go in about 2 h 50 min before you carve.

Two charts, two ovens

The calculator uses two published sources. The USDA Food Safety and Inspection Service chart gives minutes per pound at 325 °F for roasts of 4 to 6 pounds, so the time scales with weight: a 5-pound bone-in roast comes to 1 h 55 min to 2 h 05 min. The Beef Checkoff chart gives total times at 350 °F by weight band and doneness. Use whichever oven temperature your recipe calls for.

A worked comparison

At 350 °F, a 7-pound bone-in roast takes 2 h 15 min to 2 h 30 min for medium rare (removed at 135 °F) and 2 h 30 min to 3 h 00 min for medium (removed at 145 °F). A boneless 5-pound roast from the small end of the rib takes 1 h 45 min to 2 h 00 min, while the large end takes 2 h 00 min to 2 h 15 min; the chart lists the two ends separately. The hour ranges are wide on purpose: they cover differences between ovens, roast shapes and the starting temperature.

Common mistakes

Cooking to the clock and not the thermometer is the main one; the charts are planning tools. A second mistake is probing in the wrong place: the tip of the thermometer belongs in the center of the thickest part of the meat, not against a bone or in fat, both of which read differently. Third, ignoring the rise while the roast stands: the Beef Checkoff says the temperature climbs another 5 to 15 °F, so a roast left in until it reads the final temperature will end up overdone. Finally, carving at once lets the juices run out; the stand time in the charts is part of the cooking.

Sources: USDA Food Safety and Inspection Service, Beef from Farm to Table (Approximate Beef Cooking Times) and Safe Minimum Internal Temperature Chart; Beef Checkoff (Cattlemen’s Beef Board and NCBA), Oven Roasting Guidelines and Determining Doneness. Related: meat temperature chart, turkey calculator, ham cooking time calculator and pork cooking time calculator. How we check our calculators.