US: 8.5 to Europe Size 48

US: 8.5: Features an inner diameter of 18.5 $\text{mm}$ (0.728 $\text{in}$), inner circumference of 58.3 $\text{mm}$ (2.29 $\text{in}$), and standard numerical or letter ring scales optimized for women’s sizing curves.

Europe Size 48: Features an inner diameter of 15.3 $\text{mm}$ (0.602 $\text{in}$), inner circumference of 48 $\text{mm}$ (1.89 $\text{in}$).