US: 6XL to United Kingdom Size 18

US: 6XL: Corresponds to a waist/hip size of 115 $\text{cm}$ (46 $\text{in}$), waist range of 107–117 $\text{cm}$ (42.1–46.1 $\text{in}$), total strap length of 125 $\text{cm}$ (49.2 $\text{in}$), and fit classification Extended Plus.

United Kingdom Size 18: Corresponds to a waist/hip size of 95 $\text{cm}$ (38 $\text{in}$), waist range of 86–97 $\text{cm}$ (33.9–38.2 $\text{in}$), total strap length of 105 $\text{cm}$ (41.3 $\text{in}$), and fit classification Relaxed Waist / Hip.