From Official site Babywear/Kidswear The size to order corresponds to the age of the child. Age Order Size 6-24 Months Baby 2-5 Years Toddler General Size Guide The table below gives you a guide to our size descriptions. For example, the size XXL on our website would correspond to a Chest Size of 46/48" and a Waist Size of 38/40" Chest Size Waist Size Order Size 32" 24" SB (7-8yrs) 34" 26" MB (9-10yrs) 36" 28" LB (11-12yrs) 38" 30" YOUTH 40" 32" S 42" 34" M 44" 36" L 46" 38" XL 48" 40" XXL 52" - - - XXXL