US Size 5.5 = EUR Size 21 = Insole Length 13.5 cm / 5.3''
US Size 6 = EUR Size 22 = Insole Length 14 cm / 5.5''
US Size 7 = EUR Size 23 = Insole Length 14.5 cm / 5.7''
US Size 8 = EUR Size 24 = Insole Length 15 cm / 5.9''
US Size 8.5 = EUR Size 25 = Insole Length 15.5 cm / 6.1''
US Size 9 = EUR Size 26 = Insole Length 16.1 cm / 6.33''
US Size 10 = EUR Size 27 = Insole Length 16.7 cm / 6.57''
US Size 11 = EUR Size 28 = Insole Length 17.3 cm / 6.8''
US Size 11.5 = EUR Size 29 = Insole Length 17.9 cm / 7.05''
US Size 12.5 = EUR Size 30 = Insole Length 18.5 cm / 7.28''
TIP How to chose your baby's perfect size when shopping online. The figures above are the insole length. Since you don't want shoes to hurt your baby's tender feet, chose the size 0.5-1 cm 0.2-0.4'' bigger then your baby's foot length.