United Kingdom Size 8-10 to US: 18-20

United Kingdom Size 8-10: Waist range of 65–69 $\text{cm}$ (25.6–27.2 $\text{in}$), hip range of 91–95 $\text{cm}$ (35.8–37.4 $\text{in}$), lengths (Mini/Midi/Maxi): 43.5/76.5/101.5 $\text{cm}$ (17.1/30.1/40 $\text{in}$), and fit style Fitted Waist / A-Line & Straight.

US: 18-20: Waist range of 91–99 $\text{cm}$ (35.8–39 $\text{in}$), hip range of 117–125 $\text{cm}$ (46.1–49.2 $\text{in}$), lengths (Mini/Midi/Maxi): 51/84/109 $\text{cm}$ (20.1/33.1/42.9 $\text{in}$), and fit style Fitted Waist / A-Line & Straight.