General age guidelines are as follows:

Age	Violin Size
3-5	1/16 size
5-6	1/8 size
7-9	1/4 size
8-11	1/2 size
10-12	3/4 size
12 +	4/4 (full size)

"Most people measure from the arm pit to mid-palm to obtain proper arm measurement."

Arm Measurements

Arm Length	Age	Violin Size
14" to 15 3/8"	3-5 yrs	1/16-1/10
15 3/8" to 18 1/2"	3-5 yrs	1/10-1/8
18 1/2" to 20 3/8"	4-7 yrs	1/4
20 3/8" to 22 1/4"	6-10 yrs	1/2
22 1/4" to 23 5/8"	9-11 yrs	3/4
23 5/8" +	12 +	4/4 (full size)