US: 10 to Europe Size 40

US: 10: Features a foot length of 25.9 $\text{cm}$ (10.2 $\text{in}$), ball width of 9.7 $\text{cm}$ (3.82 $\text{in}$), heel height of 7.5 $\text{cm}$ (3 $\text{in}$), and 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.