US size 5.5 = Europeaan size 21 = insole length  13cm

US size 6 = Europeaan size 22 = insole length  13.5cm

US size 7 = Europeaan size 23 = insole length  14cm

US size 8 = Europeaan size 24 = insole length  14.5cm

US size 8.5 = Europeaan size 25 = insole length  15cm