US: 4-6 to United Kingdom Size 24-26

US: 4-6: Corresponds to a relaxed bust range of 84–88 $\text{cm}$ (33.1–34.6 $\text{in}$), elastic waist range of 66–70 $\text{cm}$ (26–27.6 $\text{in}$), and comfort drape classification Relaxed / Comfort Drape.

United Kingdom Size 24-26: Corresponds to a relaxed bust range of 113–117 $\text{cm}$ (44.5–46.1 $\text{in}$), elastic waist range of 95–100 $\text{cm}$ (37.4–39.4 $\text{in}$), and comfort drape classification Loose Lounge Fit.