Generally, cake shops sell cakes of 6 inches, 8 inches and 10 inches. Size and number of people to eat are:

6 inches 14.5× 14.5(cm) is suitable for 3-4 people.

8 inches 18× 18(cm) is suitable for 5-8 people.

10 inch about 2 1.5×2 1.5(cm) is suitable for 8- 12 people.

It takes 14 inches to 16 inches for about 20 people! The specific size and weight need to ask the cake shop!