Welcome to our shop! Dear customer:Because each country has different size label,so choose the correct size,need to measure the child's foot length,check size information. For example: The kids foot length 12.0 cm,need to choose the Inner length is 13.0 cm. Because the comfortable length is the foot length add about 1cm. Inner length=Foot length (Heel to toe) + 1.0cm. Choose Shoe Size 21 = Inner Length 13.0 (cm) / Suitable for Foot Length 12.0 (cm) If you have any questions,Please send Size Chart: Shoe Size 21 = Inner Length 13.0(cm) Suitable for Foot Length 12.0(cm) Shoe Size 22 = Inner Length 13.5 (cm) Suitable for Foot Length 12.5 (cm) Shoe Size 23 = Inner Length 14.0(cm) Suitable for Foot Length 13.0 (cm) Shoe Size 24 = Inner Length 14.5(cm) Suitable for Foot Length 13.5 (cm) Shoe Size 25 = Inner Length 15.0(cm) Suitable for Foot Length 14.0(cm) Shoe Size 26 = Inner Length 16.0 (cm) Suitable for Foot Length 15.0 (cm) Shoe Size 27 = Inner Length 16.5 (cm) Suitable for Foot Length 15.5 (cm) Shoe Size 28 = Inner Length 17.0(cm) Suitable for Foot Length 16.0 (cm) Shoe Size 29 = Inner Length 17.5 (cm) Suitable for Foot Length 16.5 (cm) Shoe Size 30 = Inner Length 18.0 (cm) Suitable for Foot Length 17.0 (cm)