I know that there are tons of information that are already out there for this question, but I feel that other than videos, a lot of the posts are either too wordy or hard to understand.
My head and hands were itching to design another poster for my students and parents, as well as anyone who might find this useful, so here it is!
The best way to find the right size is to actually try the violins with your teacher or a professional and trust them.
I’ll improve on this poster as we go along. Feel free to share it, hope this helps! =D