US: 12 to Europe Size 40

US: 12: Features a foot length of 27.6 $\text{cm}$ (10.85 $\text{in}$), ball width of 10.3 $\text{cm}$ (4.05 $\text{in}$), heel height of 5 $\text{cm}$ (2 $\text{in}$), and Flat-to-Medium Arch support optimized for women’s footwear.

Europe Size 40: Features a foot length of 25.4 $\text{cm}$ (10 $\text{in}$), ball width of 9.4 $\text{cm}$ (3.7 $\text{in}$), and heel height of 9 $\text{cm}$ (3.54 $\text{in}$), and Universal Arch support optimized for women’s footwear.