US: 7-W to Europe Size 31

US: 7-W: Corresponds to a foot length of 14 $\text{cm}$ (5.5 $\text{in}$), ball width of 6.3 $\text{cm}$ (2.5 $\text{in}$), grade Wide (2E), growth margin 0.8 $\text{cm}$, estimated age 3-4y, Mondopoint 140 $\text{mm}$, and fit type Toddler Wide (US 7 / Width 2E).

Europe Size 31: Corresponds to a foot length of 19 $\text{cm}$ (7.5 $\text{in}$), ball width of 7.3 $\text{cm}$ (2.85 $\text{in}$), grade Medium / Standard (D), growth margin 1 $\text{cm}$, estimated age 8-9y, Mondopoint 190 $\text{mm}$, and fit type Little Kid Medium (US 13 / Width D).