When I buy brisket for a group I buy 1 pound per person. After trimming and cooking you will lose approx 40% of product. That leaves 2/3 pound for each customer. 2/3 pound is 10.66 ounces per person. Most people eat from 6 to 8 ounce servings---this will leave you with a little bit of meat which allows you to serve "seconds" to those who wish. I have never "run out" of meat, and I usually serve "seconds."