I wear a 7 in most street shoes but will size up to 7.5 in running shoes or hiking shoes to give myself tons of toe space to avoid any chance of black toenail (been there, done that). However, in sandals, I am often a 6.5. Seems when I did try on Clarks in a store a couple of years ago, the 6.5s came the closest to fitting. Not sure if it was just that particular model or not...