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

Size Size/Age Range Chest, 1" below armhole HIP, 1" up from rib Height Weight
0-6 Months Newborn-6 months
6-12 Months 6 Months-12 Months 9.75 9.25 26.5 - 29.5" 16.5 - 22 lbs
12-18 Months 12 Months-18 Months 10.25 9.75 30 - 31.5" 22.5 - 26lbs
18-24 Months 18 Months-24 Months
One Size
2T 2 Years
3T 3 Years
4T 4 Years