Still unsure? Personally we tend to prefer a more relaxed, baggier fit and often go a size up, but hey, each to their own :) 
 
Size Woman Men

Small  

Size < 8

Height  < 5'4

Medium               

Size 8 - 10     

Height  5'6 - 5'8

Large 

Size 10 - 12  

Height  5'8 - 5'10

X Large   

Size 12 - 14 

Height  5'10 - 6'0

XX Large

Size 16 - 18  

Height  > 6'0