it depends on what league youre in
coach pitch 10 inches
minors 11 inches
majors 12 inch and so on 10 and under is 11 inches 12 and under and all the way up is 12 inches. I have seen a 14 inch softball and I think they use that in slowpitch In adult recreational leagues, women use an 11 inch ball and men use a 12 inch ball. In colder climates (Chicago, in particular) has leagues that use a 16 inch ball and no gloves during the winter.