Ice cream provides a simple yet customizable dessert option at a party, but make sure you have enough so no one goes home unsatisfied. Although you can't determine exactly how much each guest will eat, you can use basic serving sizes to create a close estimate. The age of your guests, their appetite and other refreshment choices can affect the amount of ice cream you will need.
Count the maximum number of guests who may attend. Figure each guest will eat approximately three scoops of ice cream, or about 1 ½ cups. For children's parties, especially if the ice cream is served with cake, one to two scoops may be a more accurate estimate. For big eaters, or if the ice cream is the main refreshment, you may want to figure four scoops per person to ensure there is enough.
Multiply the scoop total by 4 ounces, which is the average size of most ice cream scoops. For example, ice cream for 10 guests is 30 scoops, or 120 ounces of ice cream.
Convert the ounces needed to gallons if you are purchasing ice cream by the gallon. A true gallon contains 128 ounces of ice cream, but many containers labeled as gallons actually contain only 96 ounces. True half-gallons contain 64 ounces as opposed to the 48 ounces in some containers. If in doubt on the conversion for the brand you are purchasing, keep the measurement in ounces.
Divide the amount of ice cream needed between the different flavors you plan to provide. For example, for 10 people you need 60 ounces of vanilla and 60 ounces of chocolate if you are only providing two flavors, so 2 true gallons of each is sufficient while still providing a few extra servings.