Angulus use European shoe sizing. Some shoes fit a little differently from each other, depending on their style and linings. We recommend that you measure both feet from heel to toe and then follow the guidelines listed in the product description, where you will find the insole measurements are listed for each size. If you require any help, just email your foot measurements to firstname.lastname@example.org and let us know the styles you are looking at. We can help advise you on the correct size.