US: 12-D to United Kingdom Size 9-D

US: 12-D: Corresponds to a foot length of 29 $\text{cm}$ (11.42 $\text{in}$), ball width of 10.8 $\text{cm}$ (4.25 $\text{in}$), acceptable ball width range between 10.5–11.1 $\text{cm}$ (4.13–4.37 $\text{in}$), and fit classification Standard Width (12-D / M).

United Kingdom Size 9-D: Corresponds to a foot length of 27.2 $\text{cm}$ (10.71 $\text{in}$), ball width of 10.4 $\text{cm}$ (4.09 $\text{in}$), acceptable ball width range between 10.1–10.7 $\text{cm}$ (3.98–4.21 $\text{in}$), and fit classification Standard Width (10-D / M).