To choose the correct weight of roast, assume each guest will eat between ½ - ¾ pounds of beef. I used a 6-pounder and this generally will serve between 6-10 people. It ranges because it depends how many sides you intend to serve and the appetites of your guests. I served this for a dinner party of 6 with appetizers and 3 sides, and got 10 slices out of it. 2 folks had seconds, and I had 2 leftovers for myself.