How much chicken salad do I need to feed 20 people?
If it is the only "meat" dish you are serving and you are doing a buffet, I would go with 1/2-1 cup per person to be safe (and if you are doing a buffet) (the lower is if it is all women or women and kids, the higher if you are having a mixed group of men, women, and children).
That is 10-20 cups.
If you are serving multiple meat dishes and it is not a buffet, you can reduce that to 1/4 to 1/2 cups per person (that is 5-10 cups).
Be sure to keep the dish iced down to prevent spoilage. I like to use metal serving pans (a slightly larger one on the bottom filled with ice, rest the slightly smaller one with the chicken salad in it, on the top. Works great to keep things cool!
Questions like this are always difficult to answer as there is just not enough information to provide a good answer.
Is this just a stand alone item or is it an item among many on a buffet?
Recipes usually tell you how many servings so it's always best to find a recipe you like and increase it to how many servings you are going to need.
Figure 1/4-1/2 pound per person, depending on what else you will serve with the meal.
If making sanwiches, around 5 pounds and a minimal of 3 1/2 pounds , for up to 20 people.
If that is your main meat dish you would be safe to make the chicken salad with 20 chicken breasts.
For 1 serving - 1 cup of chicken salad (main dish).
For 20 servings - 1.25 gallons of chicken salad (main dish).
But consider the appetites and eating habits of your guests when figuring the number of servings needed.