A gallon of coffee is enough to serve about 20 people when using a small paper cup or china coffee cup that holds 6 ounces. When using a large coffee cup or other mug equal to about 8 ounces, a gallon of coffee can serve about 15 to 16 people.
Depending on the time of day that coffee is served, each guest may or may not want to have more than one serving of coffee. Generally, when coffee is served during the morning breakfast hours, people are prone to have more than one serving of coffee in a sitting and the amount planned for should be increased to reflect this.
