Starter or Appetizer If serving pumpkin soup as a starter or appetizer before the main course, a portion size of around 1/2 to 3/4 cup (120-180 ml) per person is typically sufficient.  This allows guests to enjoy the flavors without filling up too much before the main meal. 2. Main Course When pumpkin soup is intended as the main course, larger portion size is appropriate.  You can estimate serving about 1 to 1 1/2 cups (240-360 ml) per person, depending on the appetite and preferences of your guests.  Adjust the portion size based on whether you plan to serve additional dishes or sides alongside the soup.