Youth Sizes:

S - 6/8 = 37" Chest/Body Width
M - 10/12 = 39" Chest/Body Width
L - 14/16 = 42" Chest/Body Width
XL - 18/20 = 45" Chest/Body Width

Adult Unisex Sizes:

S = 49" Chest/Body Width
M = 51" Chest/Body Width
L = 53" Chest/Body Width
XL = 57" Chest/Body Width
XXL = 61" Chest/Body Width
XXXL = 65" Chest/Body Width
XXXXL = 69" Chest/Body Width
XXXXXL = 73" Chest/Body Width