S (1-2y):(Chest 20inch all around when laid flat and unstretched, stretches 3inches each way, Length 20inch)

M (3-4y): (Chest 22inch all around when laid flat and unstretched, stretches 3inches each way, Length 23inch)

L (5-6y): (Chest 24inch all around when laid flat and unstretche,d stretches 3inches each way, Length 25inch)

Baby/kid age is an estimation of fit, not all babies/kids are of the same size, so please keep in mind dimensions of clothings, rather than age groups for a more accurate fitting