United Kingdom Size 6 5/8 to US: M

Cross-market women’s hat conversion mapping 6 5/8 specifications into M.

Analyzing Hat Size Equivalence Across Markets

United Kingdom Size 6 5/8: Features a head circumference of 54.5 $\text{cm}$ (21.5 $\text{in}$ ) measured just above the brow and ears.

US: M: Features a head circumference of 56.5 $\text{cm}$ (22.2 $\text{in}$ ) measured just above the brow and ears.