To feed 100 people, serve at least 120 sandwiches according to ellenskitchen.com. Although many people only eat one sandwich, some may eat more than one. Expect to adequately serve approximately 100 people with 120 sandwiches without having much left over.
The number of sandwiches needed to serve 100 people varies depending on the type of sandwiches served. For example, if small deli sandwiches are served, more sandwiches may be needed. Serving larger sandwiches, such as heroes or subs, will probably require fewer individual units. The ingredients required to make the sandwiches also varies depending on the type of sandwich being served. Another factor that affects the number of sandwiches needed is the characteristics of those being served: 100 grown adult guests generally consume more food than 100 children.