General size guidance : 
6''(6''x 3'') feed 5-6 ppl
6'' tall (6''x5'') feed 10~12 ppl
8'' (8''x3'') feed 10~12ppl
8'' tall (8''x5'')16~18 ppl
10''(10''x3'') feed 15- 17ppl
 
 
 
 * Please be aware,  the guidance above is only use as a reference since everyone has a different eating portion. It is a standard reference for home portion, volume here is calculated as 2''x2''x4'' rectangular prism. You may serve for more people if you cut in smaller portions.