Calculator · bone-in rib roast at 325°F
Prime rib cooking time calculator
Enter the roast's weight and your dinner time for a roasting time, a start time and the rest built in.
A 7 lb bone-in prime rib at 325°F takes about 2 hr 20 min by the planner's estimate, then a 30-minute rest. USDA's chart, which cooks beef roasts to 145°F, gives 23–25 minutes per pound for 4–6 lb bone-in roasts.
- Oven
- 325°F, preheated for 15 min
- Estimate
- Based on common roasting charts for a bone-in rib roast at 325°F (165°C).
- Rest
- 30 min, loosely covered
- Prep
- 15 min before it goes in
Roasting time at 325°F
2 hr 20 min
Put it in at 2:10 PM, take it out at 4:30 PM, rest 30 min.
- 1:55 PM−3:05Preheat oven to 325°FAllow about 15 min
- 1:55 PM−3:05Prep Prime Rib15 min hands-on
- 2:10 PM−2:50Prime Rib into the oven2 hr 20 min · at 325°F
- 4:30 PM−0:30Prime Rib out of the ovenRest 30 min, loosely covered
- 5:00 PM0:00Prime Rib rested — ready to carveServe now
- 5:00 PM0:00Dinner is readyEverything should land together
Opens the planner with this prime rib and a full menu. Start checking the temperature before the time is up. Use a food thermometer. Whole cuts of beef are safe at 145°F (63°C) followed by a rest of at least 3 minutes; cook longer for your preferred doneness.
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The roast out, the oven up.
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Prime rib cooking time per pound
Prime rib times depend on how done you like it, which is why published charts disagree. The planner's estimate comes from common roasting charts for a bone-in rib roast at 325°F, which are generally aimed at medium-rare. USDA's chart is aimed at its safe minimum for beef roasts — 145°F followed by at least a 3-minute rest — and so runs longer.
| Roast | Planner estimate | USDA chart (to 145°F) |
|---|---|---|
| 4 lb | 1 hr 35 min | 1 hr 32 min to 1 hr 40 min |
| 5 lb | 2 hr | 1 hr 55 min to 2 hr 5 min |
| 6 lb | 2 hr 10 min | 2 hr 18 min to 2 hr 30 min |
| 7 lb | 2 hr 20 min | — |
| 8 lb | 2 hr 35 min | — |
| 9 lb | 2 hr 45 min | — |
| 10 lb | 2 hr 55 min | — |
| 12 lb | 3 hr 20 min | — |
USDA's beef chart only lists 4–6 lb bone-in rib roasts (23–25 minutes per pound); another USDA page gives 23–30 minutes per pound for 4–8 lb. For a boneless rib roast, USDA adds 5–8 minutes per pound. If you're cooking to 145°F or beyond, tap the roast in the planner and lengthen its time.
Whichever time you plan with, the thermometer decides. Start checking the thickest part of the roast before the time is up. USDA's safe minimum for beef roasts is 145°F (63°C) with a 3-minute rest.
What time to put the prime rib in
Count back from dinner: the rest (the planner allows 30 minutes), then the roasting time, then 15 minutes to preheat. With a full menu in one oven, the roast often goes in a little earlier so the oven can heat up for the sides while it rests. The Christmas prime rib dinner shows a full day, with the oven going from 325°F to 425°F after the roast comes out.
Questions people ask
How long does a 5 lb prime rib take at 325°F?
The planner estimates about 2 hr. USDA's chart, cooking to 145°F, gives 23–25 minutes per pound — about 1 hr 55 min to 2 hr 5 min for 5 lb. Check with a thermometer.
How long should prime rib rest?
The planner allows 30 minutes, loosely covered. USDA's minimum for beef roasts is a 3-minute rest after reaching 145°F; a longer rest makes carving easier.
Why do prime rib times vary so much between recipes?
Oven temperature and target doneness. Recipes that start hot and finish low, or roast at 250°F, use very different times from a steady 325°F. Follow your recipe's method and use a thermometer.