0000: newborn
000: 0-3 months
00: 3-6 months
0: 6-12 months
1: 12-18 months
2: 18-24 months
3: Generally for a 3 year old
4: Generally for a 4 year old
5: Generally for a 5 year old
6: Generally for a 6 year old
7: Generally for a 7 year old

Please note that there is not a standardised sizing system for baby clothing and that this is a guide only. As with adult fashion, different designers cut their garments differently and there will be variations in sizing between brands. European brands always tend to be smaller in their sizing and we recommend going up a size. If you are unsure and would like assistance, please contact us. We are only too happy to help!