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Prime Rib Cooking Time Calculator

Written by · Updated August 13, 2026

Enter your roast’s weight and target doneness to get the cooking time at 325°F and the temperature to pull it at for a perfect prime rib.

Cook time
Active cook
Rest
20 min
Total
Cook to
Pull at 120°F rare / 130°F medium-rare / 140°F medium, the temperature climbs ~5–10°F while resting

Cooked in oven at 325°F (165°C). Times are estimates, always confirm with a meat thermometer.

How long to cook prime rib

The cooking time for prime rib depends mainly on its weight and how you’re cooking it. As a starting point, the table below shows estimates in oven at 325°F (165°C) for the rare method. Add the resting time, and remember a thermometer is the only way to know it’s truly done.

Prime Rib cooking time by weight

WeightActive cook (Rare)+ Rest
2 lb 30 min 50 min
5 lb 1 hr 10 min 1 hr 30 min
8 lb 1 hr 50 min 2 hr 10 min
11 lb 2 hr 35 min 2 hr 55 min
14 lb 3 hr 15 min 3 hr 35 min
17 lb 4 hr 4 hr 20 min
20 lb 4 hr 40 min 5 hr

Safe internal temperature

Cook to: Pull at 120°F rare / 130°F medium-rare / 140°F medium, the temperature climbs ~5–10°F while resting.

Tips

  • Take the roast out of the fridge 1–2 hours before cooking so it roasts evenly.
  • For a reverse sear, cook low until 10°F below target, then blast at 500°F to crust.
  • Rest tented in foil for at least 20 minutes before slicing.
These times are estimates that vary with your oven, the starting temperature of the meat and other factors. Always verify doneness with a food thermometer before serving.

Frequently asked questions

How long to cook prime rib per pound?

At 325°F, allow roughly 14 min/lb for rare, 16 min/lb for medium-rare and 18 min/lb for medium. Pull the roast about 5–10°F below your target as it climbs while resting.

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