United Kingdom Size 11-D to US: 9-B

United Kingdom Size 11-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).

US: 9-B: Corresponds to a foot length of 26.2 $\text{cm}$ (10.31 $\text{in}$), ball width of 9.9 $\text{cm}$ (3.9 $\text{in}$), acceptable ball width range between 9.6–10.1 $\text{cm}$ (3.78–3.98 $\text{in}$), and fit classification Narrow (9-B / AA).