United Kingdom Size 9-D to US: 8-D

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).

US: 8-D: Corresponds to a foot length of 25.2 $\text{cm}$ (9.92 $\text{in}$), ball width of 10 $\text{cm}$ (3.94 $\text{in}$), acceptable ball width range between 9.7–10.3 $\text{cm}$ (3.82–4.06 $\text{in}$), and fit classification Standard Width (8-D / M).