Prime Rib (Standing Rib Roast)
cooking times
The answer
3 hr 5 min – 4 hrat 325°F
At the most common temperature, 325°F, a bone-in prime rib runs about 3 hr 5 min – 4 hr at 8 lb. Pick your temperature below for the full chart. Done is always 145°F internal.
SOURCE·USDA FSIS safe minimum internal temperatures·prime rib (standing rib roast) row of the FSIS chart·REVIEWED JUL 2026
USDA safe zone — 145°F and above
Done is a temperature, not a time. Every figure on this page is a planning range; the green band is the only part that decides. For a bone-in prime rib it opens at 145°F and a 20-minute rest.
Source—USDA Food Safety & Inspection Service safe minimum internal temperatures—doneness bands per standard cooking references—retrieved 2026-07
How this is worked out
- Anchor. Start from what USDA FSIS publishes for a bone-in prime rib — its safe minimum internal temperature of 145°F, and the FSIS roasting timetable where one exists for this cut.
- Rate. Convert the anchor into a planning rate at 325°F: 23–30 min/lb, cross-checked against at least three independently published sources.
- Scale. Multiply that rate by your weight. A 8 lb piece lands at 3 hr 5 min – 4 hr; the range is widened to cover source disagreement rather than averaged into false precision.
- First check. The first thermometer reading is set at 85% of the low end of the range — early enough that an under-reading costs nothing and a late one cannot cost the meal.
- Gate. The time is only a plan. It is not done until a food thermometer reads 145°F in the thickest part, then rests about 20 minutes. Time never overrides temperature on this site.
- Round. Every printed figure is rounded to the nearest 5 minutes; precision beyond that would be invented.
plan_low = weight_lb × 23 min/lb
plan_high = weight_lb × 30 min/lb
first_check = plan_low × 0.85
DONE ⟺ internal_temp ≥ 145°F AND rest ≥ 20 min
(USDA FSIS — the gate, not the clock)
SOURCE·USDA FSIS safe minimum internal temperatures·safe minimum for this cut·REVIEWED JUL 2026
Pick your temperature
Every temperature this chart room holds for a bone-in prime rib, each with its own worked ledger.
The whole cut, temperature by temperature
| Oven temp | Time for a 8 lb prime rib (standing rib roast) | Per pound |
|---|---|---|
| 325°F | 3 hr 5 min – 4 hr | 23–30 min/lb |
| 350°F | 2 hr 40 min – 3 hr 30 min | 20–26 min/lb |
SOURCE·USDA safe-temperature guidance·timing ranges derived, see method·REVIEWED JUL 2026
When it is actually done
145°F internal
The USDA FSIS safe minimum internal temperature for this cut is 145°F, followed by a rest of about 20 minutes. The clock estimates; the thermometer decides. Every time on this page is a planning range, not a doneness test.
SOURCE·USDA FSIS safe minimum internal temperatures·prime rib (standing rib roast) row of the FSIS chart·REVIEWED JUL 2026
Doneness temperatures
| Doneness | Internal temp | |
|---|---|---|
| Rare | 120–125°F | below the USDA minimum |
| Medium-rare | 130–135°F | below the USDA minimum |
| Medium | 135–145°F | |
| Medium-well | 145–155°F | |
| Well done | 155°F+ |
USDA FSIS recommends a minimum of 145°F with a 20-minute rest for whole cuts. Rare and medium-rare sit below that guideline — a personal choice many cooks make with fresh, well-handled meat, listed here because these are the temperatures cookbooks and restaurants use.
SOURCE·Standard published cooking references·doneness bands·REVIEWED JUL 2026
What the ledger does not tell you
- The low end of each range lands medium-rare, the high end medium — decide your pull temperature before you start, not at the oven door.
- A large roast carries over 5–10°F while resting; pull it that far below your target.
- Many cooks finish with a 500°F blast for the last 8–10 minutes (or start with one) for the crust — the per-pound time barely changes.
- Bones act as insulation: a boneless ribeye roast of the same weight cooks slightly faster.
The clock tells you when to start looking. The thermometer tells you when to stop.
