A full sheet cake provides approximately 70 to 80 servings, depending on the cake's actual measurements and the serving size. The average full sheet cake measures approximately 14 by 22 to 18 by 24 inches. The standard serving size measures 2 by 2 inches.
To estimate the amount of cake needed, consider the type of event, the number of guests and the full dessert menu. People tend to eat less cake at formal events than at informal gatherings, and some guests may not eat cake due to dietary restrictions. Offering other types of desserts, such as fresh fruit, cookies or brownies, reduces the amount of cake needed. When ordering cake from a bakery, place orders at least 24 to 48 hours in advance, and provide specific details about any requested colors, icing flavors and additional decorations.