US: 6-8.5 to Europe Size 18-20
Cross-market children’s socks, tights, hosiery, leg warmers, and dance tights sizing conversion mapping 6-8.5 specifications into 18-20.

Analyzing Size Equivalence Across Markets
US: 6-8.5: Corresponds to a foot length of 20 (7.9 ), matching US shoe size 13-3, and age range 84–120 months.
Europe Size 18-20: Corresponds to a foot length of 11.5 (4.5 ), matching US shoe size 3-4, and age range 6–12 months.