Kids Footwear Full Size Chart With Age Group Reference
UK / India EURO US Length (CM) Age Group
0 16 1 8.9 0- 02 Month
1 17 2 9.5 02- 04 month
2 18 3 10.5 04-06 Months
3 19 4 11.4 06-09 months
4 20 5 12.1 09-1.2 Yrs
4.5 21 5.5 12.45 09-1.2 Yrs
5 22 6 13 1.2-1.6 Yrs
6 23 7 14 1.6 -2.5 Yrs
7 24 8 14.6 2.5 - 3 Yrs
8 25 9 15.6 3 – 4 Yrs
8.5 26 9.5 16.0 3 – 4 Yrs
9 27 10 16.5 4 – 5 Yrs
10 28 11 17.1 5  -6 Yrs
10.5 29 11.5 17.5 5  -6 Yrs
11 30 12 18.1 6 -7 Yrs
12 31 13 19.1 7  - 8 yrs
13 32 1 19.7 8 – 9 Yrs
1 33 2 20.3 9 -10 Yrs
2 34 3 21.6 10 -11 Yrs
2.5 35 3.5 21.9 11- 11.5 Yrs
3 36 4 22.9 11.5 -12 Yrs
4 37 5 23.2 12 - 13 Yrs
5 38 6 24.1 13- 14 yrs
6 39 7 24.8 13- 14 yrs
 NOTE: This size chart is a guidance and not a thumb rule.

Considering the practical designing and construction  of the footwear there is a tolerance/flexibility in measurement upto 10%, please  consider this while selecting/buying/suggesting a right fit shoe.
Footwear anatomy varies from child to  child , so better try the size for desired comfort.
Suggest for kids you should buy a comfortably fit size or bit roomy up to next size.