United Kingdom Size 20 to US: L

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: 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.