United Kingdom Size 20 to US: XL

United Kingdom Size 20: Corresponds to a waist/hip size of 100 $\text{cm}$ (40 $\text{in}$), waist range of 91–102 $\text{cm}$ (35.8–40.2 $\text{in}$), total strap length of 110 $\text{cm}$ (43.3 $\text{in}$), and fit classification Expanded / Plus.

US: XL: Corresponds to a waist/hip size of 90 $\text{cm}$ (36 $\text{in}$), waist range of 81–91 $\text{cm}$ (31.9–35.8 $\text{in}$), total strap length of 100 $\text{cm}$ (39.4 $\text{in}$), and fit classification Relaxed Waist / Hip.