US: M to Europe Size 15

US: M: Corresponds to a wrist circumference baseline of 16.5 $\text{cm}$ (6.5 $\text{in}$), bracelet length of 18 $\text{cm}$ (7.1 $\text{in}$), and fit classification Standard / Regular.

Europe Size 15: Corresponds to a wrist circumference baseline of 14 $\text{cm}$ (5.5 $\text{in}$), bracelet length of 15 $\text{cm}$ (5.9 $\text{in}$), and fit classification Snug / Compact.