Please notice that the size above is inner length. And there maybe 0-1cmerror due to the measure by hand. The size you need=length of your child's feet+1~2cmPlease choose the bigger size for the children feet grow very fast.US size 7=CN size 23(shoes inner length 14.5cm) US size 8=CN size24(shoes inner length 15cm) US size 9=CN size 25(shoes inner length 15.5cm) US size 9.5=CN size 26(shoes inner length 16cm) US size 10=CN size 27(shoes inner length 16.6cm) US size 11=CN size 28(shoes inner length 17.2cm) US size 11.5=CN size 29(shoes inner length 17.8cm) US size 12=CN size 30(shoes inner length 18.4cm) US size 13=CN size 31(shoes inner length 19cm) US size 1=CN size 32(shoes inner length 19.6cm) US size 2=CN size 33(shoes inner length 20.2cm) US size 3=CN size 34(shoes inner length 20.8cm) US size 3.5=CN size 35(shoes inner length 21.4cm) US size 4=CN size 36(shoes inner length 22cm)