S (1-2y): chest 48cm/19inches all around, total length 48cm

M (3-4y): chest 52cm/20inches total length 54cm

L (5-6y): chest 56cm/22inches all around, total length 60cm

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