Manufacturer's size guide:
Size
Bust
Waist
Teen
32-34"
22-24"
X-Small
32-34"
22-24"
Small
33-35"
25-26"
Medium
36-38"
27-30"
Large
38-40"
31-34"
Standard
36-38"
27-30"
Plus
42-44"
35-38"