United Kingdom Size 18 to US: 8-10

United Kingdom Size 18: Waist range of 83–90 $\text{cm}$ (32.7–35.4 $\text{in}$), hip range of 109–116 $\text{cm}$ (42.9–45.7 $\text{in}$), lengths (Mini/Midi/Maxi): 49/82/107 $\text{cm}$ (19.3/32.3/42.1 $\text{in}$), and fit style Fitted Waist / A-Line & Straight.

US: 8-10: Waist range of 70–75 $\text{cm}$ (27.6–29.5 $\text{in}$), hip range of 96–101 $\text{cm}$ (37.8–39.8 $\text{in}$), lengths (Mini/Midi/Maxi): 45/78/103 $\text{cm}$ (17.7/30.7/40.6 $\text{in}$), and fit style Fitted Waist / A-Line & Straight.