Group Description	Pounds per person
All men- Louisiana	4.5 - 5 lbs.
Mixed group Men-Women-Children Louisiana natives	3.5 lbs. (men / women only + 1/2 lb)
Mixed group Men-Women-Children Non-louisiana natives	3.0 lbs (men / women only  + 1/2 lb)
The above guidelines are by no way "an exact science"; however, after having done many crawfish boils, the above guidelines have always served me well. You may want to also consider other things being served......potatoes, onions, corn, andouille, etc. You should also weigh the number of adults vs. the number of children and whether or not they are "first-timers".