Work out how long to roast a prime rib for rare, medium-rare or medium. Enter the weight or number of ribs, pick a method (classic sear then 325°F, reverse sear, or the 500°F closed-oven method) and get the oven time, pull temperature, rest and a timeline to your serving time.
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Size of roast
Method
Enter your values to see the result.
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How to use the Prime Rib Cooking Time Calculator
Enter the roast weight, or choose the number of ribs if you are buying by the bone.
Pick a doneness: medium-rare is the classic choice for prime rib.
Choose a method: classic sear-then-roast, reverse sear, or the 500°F closed-oven method.
Set your serving time to get when to temper, preheat, roast, rest and carve.
Use a probe thermometer and pull the roast at the temperature shown; times are estimates.
Prime rib cooking times and temperatures
Doneness
Pull at (standard)
Final temp after rest
Sear + 325°F
Reverse sear 250°F
500°F closed oven
Rare
115–118°F
125°F (52°C)
13–15 min/lb
≈ 28 min/lb
4 1/2 min/lb
Medium-rare
125–128°F
135°F (57°C)
15–17 min/lb
≈ 32 min/lb
5 min/lb
Medium
135–138°F
145°F (63°C)
17–20 min/lb
≈ 36 min/lb
6 min/lb
Medium-well
140–143°F
150°F (66°C)
≈ 20 min/lb
≈ 39 min/lb
6 1/2 min/lb
Well done
150–153°F
160°F (71°C)
≈ 22 min/lb
≈ 43 min/lb
7 min/lb
The calculator multiplies the roast weight by these minutes per pound. A rib roast weighs roughly 2 lb per bone. Carryover cooking is larger for big roasts, so the pull temperature is 10°F under target above 8 lb and 7°F under for smaller roasts. Thickness, starting temperature and your oven all change real times, so start checking with a probe thermometer at about three-quarters of the estimate.
Which method should you choose?
Sear then 325°F: the classic standing rib roast. Reliable, gives drippings for jus and Yorkshire pudding, but leaves a thicker band of well-done meat under the crust.
Reverse sear: the most even pink from edge to center and a flexible rest that can absorb timing delays. Needs the most time and an oven-safe probe.
500°F closed oven: hands-off and frees the oven-top, but you cannot check without opening the door, so it is least forgiving. Best for 4–9 lb roasts that start at room temperature.
For all methods: dry-brine with kosher salt (about 1/2 tsp per lb) a day ahead, uncovered in the fridge, roast bone side down so the ribs act as a rack, and slice against the grain about 1/2–3/4 in thick.
Frequently asked questions
How long do I cook prime rib per pound?
With a 15-minute sear at 450°F followed by 325°F, plan on about 13-15 minutes per pound for rare, 15-17 for medium-rare and 17-20 for medium. A 4-rib, 8 lb roast cooked to medium-rare takes about 2 hours 10 minutes. Always go by internal temperature.
What temperature should I pull prime rib for medium-rare?
Pull it at about 125-128°F. The temperature keeps rising 5-10°F while it rests (more for large roasts), finishing at about 130-135°F. For rare pull at 115-118°F, and for medium at 135-138°F.
What is the 500 degree prime rib method?
Put a room-temperature roast into a fully preheated 500°F oven for about 5 minutes per pound (for medium-rare), then turn the oven off and leave the door closed for exactly 2 hours. It works best for 4-9 lb roasts in ovens that hold heat well. Check the temperature before serving; if it is under target, finish it in a 350°F oven.
How does reverse sear prime rib work?
Roast low (225-250°F) until about 5°F below your target, rest it 30 minutes or more, then blast it at 500°F or higher for 8-10 minutes to crisp the outside. The meat cooks very evenly from edge to center with almost no gray band. It takes longer: roughly 30-35 minutes per pound at 250°F for medium-rare.
How many people does a prime rib feed?
Plan about 1 lb per person for a bone-in roast (one rib feeds about two people) and about 1/2 lb per person for boneless. A 3-rib roast of about 6 lb serves 6; a full 7-rib rack serves 12-14.
How long should prime rib rest?
Rest a seared-then-roasted prime rib 20-30 minutes, loosely tented with foil, before carving. A reverse-seared roast rests before the final sear and can be carved right after it. Resting lets the temperature even out and keeps juices in the meat.
Is medium-rare prime rib safe?
USDA lists 145°F with a 3-minute rest as the safe minimum for whole cuts of beef. Many cooks serve prime rib rarer than that because bacteria are mainly on the surface of an intact roast, which the searing heat kills. Choose medium if you want to follow the USDA guideline.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.