US: 16-18 to United Kingdom Size 20-22

US: 16-18: Corresponds to a relaxed bust range of 105–109 $\text{cm}$ (41.3–42.9 $\text{in}$), elastic waist range of 87–92 $\text{cm}$ (34.3–36.2 $\text{in}$), and comfort drape classification Loose Lounge Fit.

United Kingdom Size 20-22: Corresponds to a relaxed bust range of 105–109 $\text{cm}$ (41.3–42.9 $\text{in}$), elastic waist range of 87–92 $\text{cm}$ (34.3–36.2 $\text{in}$), and comfort drape classification Loose Lounge Fit.