There was no size chart for youth sizes, so I would follow the other products offered by the same brand.
 
Youth Size Chart
 
Brand Size
US Size
Height (in)
Waist (in)
Hip (in)
XS
6
47
22
25.5
S
7
50.5
23.5
27.3
M
8/10
54
25
29.1
L
12
57.5
26.5
30.9
XL
14
60
27.5
32.7
XXL
16
62.5
28.5
34.5
 
Adult Size Chart
 
Brand Size
US Size
Bust (in)
Cup
X-Small
XS
32.5
30 A/B/C
Small
S
34.5
32 A/B/C 30 D/DD
Medium
M
36.5
34 A/B/C 32 D/DD
Large
L
38.5
36 A/B/C 34D/DD
X-Large
XL
40.5
38 A/B/C 36D/DD