US: 9-11 to Europe Size 21-23
Cross-market children’s socks, tights, hosiery, leg warmers, and dance tights sizing conversion mapping 9-11 specifications into 21-23.

Analyzing Size Equivalence Across Markets
US: 9-11: Corresponds to a foot length of 23 (9.1 ), matching US shoe size 4-7, and age range 120–168 months.
Europe Size 21-23: Corresponds to a foot length of 13.5 (5.3 ), matching US shoe size 5-7, and age range 12–24 months.