I have to second this comment. Also having a bit extra never hurt for let overs or seconds.I always figure 6 ounces of sandwich meat per sandwich. So 100 sandwiches would be 600 ounces of meat or 37.5 pounds. So with roughly 50% shrinkage you need to start with about 75 to 80 lbs of raw pork butt. Sounds like about 8 to 10 average pork butts.