United Kingdom Size 31–33 to US: XS (26–28)

United Kingdom Size 31–33: Corresponds to a waist stretch range of 78.7–83.8 $\text{cm}$ (31–33 $\text{in}$), hip circumference of 96.5 $\text{cm}$ (38 $\text{in}$), thigh clearance of 55 $\text{cm}$ (21.7 $\text{in}$), and fit style Briefs, Boxers & Boxer Briefs.

US: XS (26–28): Corresponds to a waist stretch range of 66–71 $\text{cm}$ (26–28 $\text{in}$), hip circumference of 84 $\text{cm}$ (33 $\text{in}$), thigh clearance of 48 $\text{cm}$ (18.9 $\text{in}$), and fit style Briefs, Trunks & Boxer Briefs.