US: 12-D to United Kingdom Size 6-B

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 6-B: Corresponds to a foot length of 24.5 $\text{cm}$ (9.65 $\text{in}$), ball width of 9.6 $\text{cm}$ (3.8 $\text{in}$), acceptable ball width range between 9.3–9.8 $\text{cm}$ (3.65–3.85 $\text{in}$), and fit classification Narrow (7-B / AA).