An 8-inch birthday cake is 20 centimeters in diameter, enough to serve 3-5 people.

The size of an 8 inch cake depends on what you make it with. Usually there are buttercream, mousse cake, cheesecake, chocolate cake, ice cream cake and fruit cake. Cakes made with different ingredients have different flavors. If everyone likes a certain kind of cake, then an 8-inch cake can be divided among up to 5 people.

Expanded Information:

If the cake is eaten after a meal, the cake is large enough for 6-8 people.

If the eating is larger, then an eight-inch cake is big enough for four people. an eight-inch cake is not that big. If someone has a sweet tooth and doesn't have enough food to eat at the table, this eight-inch cake is big enough for four people.

So the number of people who can eat an 8-inch cake is variable. But it is generally a formality to eat birthday cake as a dessert, when many people are already full. At that point, as long as no one can share a piece of cake, it should make sense to divide the eight-inch cake among six people.