This is the size guide for Xero Shoes boys' sandals.

Remember that the recommended excess for sandals is between 0.5 and 0.8 cm.

Size	Interior Length	Broad
30	18.6	8.5
31	19.3	8.7
32	20	8.9
33	21	9.1
34	21.7	9.3
36	22.4	9.5