United Kingdom Size 12 to US: L

United Kingdom Size 12: Corresponds to a waist/hip size of 80 $\text{cm}$ (32 $\text{in}$), waist range of 71–81 $\text{cm}$ (28–31.9 $\text{in}$), total strap length of 90 $\text{cm}$ (35.4 $\text{in}$), and fit classification Standard Waist / Hip.

US: L: Corresponds to a waist/hip size of 85 $\text{cm}$ (34 $\text{in}$), waist range of 76–86 $\text{cm}$ (29.9–33.9 $\text{in}$), total strap length of 95 $\text{cm}$ (37.4 $\text{in}$), and fit classification Standard Waist / Hip.