For 6 people, plan on about a 6–7 lb bone-in prime rib or about a 4.5–5 lb boneless roast, assuming prime rib is the main course at a sit-down meal.

Quick Scoop

  • Bone-in prime rib for 6 :
    • Rule of thumb is about 1 lb of raw, bone-in prime rib per adult for a standard dinner.
* Many butchers and roasting charts note that a 3-bone roast (often around 6–7 lb) comfortably feeds 5–6 adults.
  • Boneless prime rib for 6 :
    • Common guidance is 1/2–3/4 lb per adult for boneless prime rib, so 3–4.5 lb technically “works,” but most hosts aim closer to 3/4–1 lb for generous portions and some fat trimming.
* That puts you in the 4.5–5 lb boneless range for 6 people.

When to Size Up

  • If your guests have hearty appetites, you want thicker slices, or you’d like leftovers for sandwiches, go a bit larger:
    • Bone-in: 7–8 lb (still 3 ribs, but on the larger side).
* Boneless: 5.5–6 lb.
  • If you’re serving many rich sides (potatoes, multiple veggies, bread, appetizers) and lighter eaters, you can get away with the lower end of the range (about 5.5–6 lb bone-in or 4–4.5 lb boneless).

Simple Rule To Remember

  • Bone-in: 1 lb per person (about 2 people per rib; 3 ribs for 6 guests).
  • Boneless: 3/4 lb per person for comfortable portions (round up a bit if you love leftovers).

Information gathered from public forums or data available on the internet and portrayed here.