My largest pan is 12/17. Someone wants me to make a cake for 30 adults and 30 children. Will this pan be big enough? Double layer cake.
According to Wilton, a 12x18x4 layer cake will provide 72 party size (1-1/2x2x4)) servings:
or 98 wedding size (1x2x4) servings:
A single layer 12x18x2 cake will provide 36 party size (3x2x2) servings or 49 wedding size (2x2x2) servings.
When people tell me they have 30 people coming, I usually make a 12 x 18 (half sheet) size cake and they usually have a reasonable amount of leftovers because not everyone eats cake.