What's the Euro to US size?

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This chart lists the suggested ages for European sizes:

Infants/Toddlers sizes:
50cm=newborn
56cm=0-3mo
62cm=3-6mo
68cm=6-9mo
74cm=9-12mo
80cm=12-18mo
86cm=24mo-2T
92cm=2-3T
98cm=3-4T
104cm=4
110cm=5
116cm=6

Girls' and Boys' sizes:
122cm = 7
128cm = 8
134cm = 9
140cm = 10
146cm = 11
152cm = 12
158cm = 13
164cm = 14
170cm = 15
176cm = 16

then go on to adult sizes.

You can also find helpful information here in the Downloads.