US: 3-6M to Europe Size 49-51
Cross-market children’s hats, beanies, caps, sun hats, and ear-flap hats apparel conversion mapping 3-6M specifications into 49-51.

Analyzing Size Equivalence Across Markets
US: 3-6M: Corresponds to a head circumference baseline of 42.5 (16.7 ) and age range 3–6 .
Europe Size 49-51: Corresponds to a head circumference baseline of 50 (19.7 ) and age range 24–48 .