Prime rib cooking time calculator
Weight, doneness and oven method in; roasting time and the exact temperature to pull the roast out. The rest takes it the last few degrees.
Roast at 325°F for about
2 hr 40 min
Pull at 125°F (52°C). After a 20-minute rest it should settle near 133°F, medium-rare.
- Minutes per pound
- 20
- Feeds
- 8 (2 per rib)
- Out of the fridge
- 1–2 hours before
- Rest
- 20 min, loosely tented
Carryover cooking: why you pull the roast early
When the roast comes out, its outer layers are far hotter than the centre, and that heat keeps moving inward. Step through the rest to watch the core climb. A hotter oven stores more heat in the outer layers, so the rise is bigger.
| Doneness | Pull from oven | After resting | Looks like |
|---|---|---|---|
| Rare | 115°F / 46°C | 122°F | Cool red centre |
| Medium-rare | 125°F / 52°C | 132°F | Warm red-pink centre |
| Medium | 135°F / 57°C | 142°F | Pink centre |
| Medium-well | 145°F / 63°C | 152°F | Slightly pink |
Prime rib cooking time per pound
At 325°F a bone-in standing rib roast takes roughly 17 minutes per pound for rare, 20 for medium-rare and 23 for medium. Boneless roasts are thinner and take a little less. These are starting points: roasts differ in shape and starting temperature, so a probe thermometer left in the centre is what tells you when to stop.
The USDA’s safe minimum for whole beef roasts is 145°F with a three-minute rest, which is medium. Rare and medium-rare are a personal choice many cooks make for intact beef roasts, since bacteria sit on the surface and the outside gets far hotter than the centre.
Reverse sear, step by step
- Season the roast generously with salt, ideally the day before, and leave uncovered in the fridge.
- Roast at 225°F until the centre is 10°F under your final target.
- Rest 30 minutes (the low oven means very little carryover).
- Blast at 500°F for 8–12 minutes to brown the crust, then carve immediately.
Questions cooks ask
How long to cook a 10 lb prime rib?
At 325°F, about 3 to 3½ hours for medium-rare (around 20 minutes per pound), pulling it at 125°F.
What temperature do I pull prime rib for medium-rare?
Around 125°F. It rises to about 130–135°F as it rests.
How much prime rib per person?
Allow about 1 lb bone-in (roughly one rib for two people) or ½ lb boneless per person.
Should prime rib be covered in the oven?
No. Roast it uncovered, fat side up, on the bones or a rack so the crust browns.