The number of ribs in a roast is a more reliable way to estimate serving sizes than weight alone because rib sizes vary by animal. One bone serves two people .
Add an extra 1/4 pound per person to your calculation if you want enough for sandwiches the next day. 2. Estimating by Rib Count
Portion planning depends heavily on whether you choose a bone-in or boneless cut:
A full prime rib consists of seven ribs (ribs 6 through 12). Butchers often split this into two distinct sections: