When trying to decide between two sizes, choose the larger size for a better fit.

Preemie (P)13.751414up to 17up to 5 lbs
Newborn (NB)15.51616up to 215-8 lbs
3M (3M)1717.517.521-248-12 lbs
6M (6M)1818.518.524-2612-16 lbs
9M (9M)18.5191926-2916-20 lbs
12M (12M)1919.519.529-3120-24 lbs
18M (18M)1.7520.2520.2531-3324-27 lbs
24M (24M)20.5212132-3427-30 lbs
2T (2T)20.5212133-3528-32 lbs
3T (3T)2121.52235-3832-35 lbs
4T (4T)22222338-4135-39 lbs
*in inches
Baby Costume Sizing Chart Diagram