Prime rib calculator
How big a roast to buy, how long it takes for the doneness you want, the temperature to pull it at, and a countdown from salting it to carving. Classic roast or reverse sear. No sign-up.
Your prime rib countdown
- Thursday, Dec 24 · 9:00 amSalt the roastAll over, then uncovered on a rack in the fridge so the surface dries. ATK salts 24 to 96 hours ahead, Serious Eats 1 to 4 days: any time from now up to 3 days earlier works.
- Friday, Dec 25 · 2:20 pmPreheat to 350°F (177°C)The roast goes in straight from the fridge: the timetables assume it starts at fridge temperature, and ATK's and Serious Eats' prime ribs skip the counter too. Fat side up in a roasting pan, bones down as a natural rack.
- Friday, Dec 25 · 2:40 pmRoast in the oven1 hr 50 min to 2 hr at this weight, scaled from the beef checkoff's times. This start uses the long end, so a slow roast is still on time.
- Friday, Dec 25 · 4:30 pmStart checking the temperatureProbe the centre of the thickest part, away from the bone. Pull it at 120°F (49°C); it climbs about 10°F while it rests, to 130°F (54°C), medium rare. That is below USDA's safe minimum of 145°F (63°C) with a 3-minute rest; most cooks accept it for a whole roast, but the choice is yours. If it gets there early, tent it with foil and let it wait: ATK rests a prime rib for up to 75 minutes.
- Friday, Dec 25 · 4:40 pmOut of the oven, let it rest20 minutes, loosely tented with foil (the checkoff rests it 15 to 20). Make the jus from the pan drippings now.
- Friday, Dec 25 · 5:00 pmCarve and serveCut along the ribs to lift the bones off in one piece, then slice the eye across the grain; serve the ribs on the side.
- Friday, Dec 25 · 6:40 pmLeftovers in the fridge by nowFSIS: nothing cooked left out more than 2 hours (1 above 90°F, 32°C). Slice it and chill it in shallow containers. It keeps 3 to 4 days in the fridge and 2 to 3 months in the freezer; eat it cold or reheat it to 165°F (74°C).
Times are approximate: the thermometer, not the clock, says when it is done. For the pan juices, see how to make au jus.
Prime rib cooking times by weight
The beef checkoff's table, at 350°F (177°C) from the fridge, pulled at 135°F (57°C) for its medium rare and 145°F (63°C) for its medium; the roast rises about 10 to 15°F while it rests. Times are approximate: finish with a thermometer.
| Bone-in roast | Pull at 135°F | Pull at 145°F |
|---|---|---|
| 4 to 6 lb (2 ribs) | 1¾ to 2¼ hr | 2¼ to 2¾ hr |
| 6 to 8 lb (2 to 4 ribs) | 2¼ to 2½ hr | 2½ to 3 hr |
| 8 to 10 lb (4 to 5 ribs) | 2½ to 3 hr | 3 to 3½ hr |
| Boneless ribeye roast | Pull at 135°F | Pull at 145°F |
|---|---|---|
| 3 to 4 lb | 1½ to 2 hr | 1¾ to 2¼ hr |
| 4 to 6 lb | 1¾ to 2¼ hr | 2 to 2½ hr |
| 6 to 8 lb | 2 to 2½ hr | 2¼ to 2¾ hr |
Prime rib temperature chart
Serving temperatures are America's Test Kitchen's. The pull temperature is where it leaves the oven; the time is for a 7 lb bone-in roast at 350°F.
| Doneness | Serve at | Pull, 350°F oven | Pull, reverse sear | 7 lb, 350°F |
|---|---|---|---|---|
| Rare | 125°F (52°C) | 115°F (46°C) | 120°F (49°C) | 1 hr 40 min to 1 hr 55 min |
| Medium rare | 130°F (54°C) | 120°F (49°C) | 125°F (52°C) | 1 hr 50 min to 2 hr |
| Medium | 140°F (60°C) | 130°F (54°C) | 135°F (57°C) | 2 hr 5 min to 2 hr 20 min |
| USDA safe minimum | 145°F (63°C) | 135°F (57°C) | 140°F (60°C) | 2 hr 15 min to 2 hr 30 min |
| Medium well | 150°F (66°C) | 140°F (60°C) | Not this way | 2 hr 25 min to 2 hr 45 min |
| Well done | 160°F (71°C) | 150°F (66°C) | Not this way | 2 hr 40 min to 3 hr 10 min |
Where the numbers come from
The oven times are the beef checkoff's roasting guidelines (Beef. It's What's For Dinner): ribeye roasts at 350°F, bone-in to 10 lb and boneless to 8 lb, pulled at 135°F or 145°F. It is the only published table that times prime rib by doneness. USDA FSIS's own charts time everything to its 145°F (63°C) minimum at 325°F (163°C), 23 to 25 minutes a pound for a 4 to 6 lb bone-in roast (Beef from Farm to Table), so they only fit well-done cooks. For every other pull temperature the calculator scales the checkoff's times with Newton's law of heating (how fast the centre closes the gap to the oven); that step is ours, and the countdown says when a time is scaled.
Doneness follows America's Test Kitchen's serving temperatures and its advice to take a roast off 5 to 15 degrees early; Serious Eats' prime rib guide agrees from medium rare up. Reverse sear is Serious Eats' recipe. Salting 24 to 96 hours ahead is ATK's Best Prime Rib. Portions: Serious Eats' pound a head, the checkoff's "1 rib for every 2 people", Foodie and Wine's ½ to ¾ lb boneless, and Certified Angus Beef's extra pound for leftovers. Thawing, the 2-hour rule and leftovers are FSIS's, and so is the warning about mechanically tenderized beef. The 20-minute preheat is our allowance.
Once it is carved, a slice of prime rib on a warm plate with a spoon of jus is most of the plating done. Our au jus guide makes the jus from the pan, and the guide to plating food covers the rest.
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Prime rib questions, answered
How much prime rib per person?
About 1 lb (450 g) of bone-in roast a person, which is one rib for every two guests: that is Serious Eats' rule and the beef checkoff's. With plenty of other food on the table, ¾ lb (340 g) a person, one rib for three, is enough. Boneless, plan on ½ to ¾ lb (225 to 340 g) a person. So eight guests need a 8 lb, 4-rib roast.
How long to cook prime rib per pound?
At 350°F (177°C) a bone-in prime rib takes about 15 to 27 minutes a pound pulled at 135°F, fewer per pound the bigger it is: the beef checkoff gives 1¾ to 2¼ hr for 4 to 6 lb and 2½ to 3 hr for 8 to 10 lb. Boneless takes about the same total time at a lower weight. Per-pound rules are rough, and Serious Eats warns that any chart varies with the roast's shape and your oven, so always finish with a thermometer.
What temperature do I pull prime rib for medium rare?
For medium rare the way restaurants serve it, 130°F (54°C) at the table, take it out of a 350°F oven at about 120°F (49°C): America's Test Kitchen pulls at 115 to 120°F and the roast climbs 5 to 15 degrees as it rests. After a reverse sear, pull at about 125°F (52°C), because a low oven leaves very little carryover. The beef checkoff pulls at 135°F and calls the resulting 145°F medium rare.
Is medium-rare prime rib safe?
USDA's safe minimum for beef roasts is 145°F (63°C) with a 3-minute rest, so medium rare as most cooks mean it, 130°F (54°C), is below it. In an intact roast, bacteria sit on the surface, which the oven heats far past that, and most recipes accept a pink centre; the calculator shows the USDA level as its own choice and marks everything below it. Cook to 145°F for anyone pregnant, very young, elderly or with a weak immune system, and always if the label says mechanically or blade tenderized, because the needles push surface bacteria inside.
Should prime rib come to room temperature first?
No. The roasting tables assume a roast straight from the fridge, and neither America's Test Kitchen's nor Serious Eats' prime rib recipe sits it on the counter; ATK found an hour on the counter warmed a steak only to 52°F (11°C). USDA says perishable food should not be left out for more than 2 hours, which a counter rest plus carving eats into.
How long should prime rib rest?
15 to 20 minutes after a 350°F roast, loosely tented with foil (the beef checkoff; Certified Angus Beef rests it 20). After a low-oven reverse sear it can rest anywhere from 30 minutes to 1½ hours before the final sear, which is what makes that method easy to time.
What is the reverse sear method?
Roast in a low oven until the centre is almost done, rest, then blast the outside in a very hot oven just before serving. Serious Eats roasts at 250°F (121°C) for 3½ to 4 hours, rests it 30 to 90 minutes and sears it at 500 to 550°F (260 to 288°C) for 6 to 10 minutes; the meat is evenly pink edge to edge. USDA does not recommend oven temperatures below 325°F (163°C), so it is outside federal guidance, and the calculator says so.
How many ribs are in a prime rib, and which end is better?
A whole standing rib roast has seven ribs, the 6th to the 12th, and weighs 14 to 22 lb or more trimmed (USDA's purchase spec). Butchers usually sell it as two roasts: the first cut, or small or loin end (ribs 10 to 12), has one big eye of meat and less fat; the second cut, or chuck end (ribs 6 to 9), has more small muscles and fat. Each rib adds about 2 lb.
How long do prime rib leftovers last?
Refrigerate within 2 hours of it leaving the oven (1 hour above 90°F, 32°C), sliced into shallow containers. It keeps 3 to 4 days in the fridge or 2 to 3 months frozen (USDA). Eat it cold, or reheat it to 165°F (74°C).
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