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Size Guide

Our sizes are expressed as the upper end of the age range for which a size is designed.  As such, a size 6M is for babies between three and six months of age.

Please use a tape measure to determine the approximate measurement of your baby in Millie & Sebby clothing.  In cases where a baby is in between sizes, go with the larger size.


Size Weight (lbs) Height (in) Weight (kg) Height (cm)
NB 6.0-9.0 up to 21.5 2.7-4.1 up to 54.6
3M 9.0-12.5 21.5-24.0 4.1-5.7 54.6-61.0
6M 12.5-17.0 24.0-26.5 5.7-7.7 61.0-67.3
9M 17.0-21.0 26.5-28.5 7.7-9.5 67.3-72.4