United Kingdom Size 50 to US: 34

United Kingdom Size 50: Corresponds to a waist size of 125 $\text{cm}$ (50 $\text{in}$), total strap length of 140 $\text{cm}$ (55.1 $\text{in}$), and recommended fit classification Extended / Plus.

US: 34: Corresponds to a waist size of 85 $\text{cm}$ (34 $\text{in}$), total strap length of 100 $\text{cm}$ (39.4 $\text{in}$), and recommended fit classification Standard / Regular.