Please check individual products for specific sizing, as different suppliers have different measurements. I am currently working with two suppliers - Jefferies Socks and maMer Sydney.
Generally speaking I would advise that if you are concerned about the item being too small, best to go the next size up.
Jefferies Socks Size Chart
maMer Sydney Sizing
65cms - 0-6 months.
75cms - 6-12 months - product is approximately 54cms long.
85cms - 1-2 years.
95cms - 3-4 years.
105cms - 5-6 years.
120cms - 7-8 years.
Please note that this product is very generous in sizing.