Catering planner version 3.03 available now from http://www.bbq-review.com/forum/viewtopic.php?t=10 in the top post on this thread are the new versions of the Excel spreadsheet (.xls) and a Zipped version of the spreadsheet (.zip).
[FONT="]Now using the number of meats and the number of sides with an algorithm to calculate multiple meat / side figures.[/FONT]
Algoritwha:shock:t! Just kidding really a neat tool!
About 90 lbs raw equals about 45 lbs cooked equals 3/4 lb food per person.
If the briskets are flats you could start with a little less.
I'll third that.I'm with Ray. If its a buffet, plan on 3/4 a person (cooked). You might get by with 1/2, but I wouldn't risk it.
If you can control portions, then you might get by with 1/4-1/3 per sandwich.