FiveFingers Size Guide

EU US UK AUS / NZ Length
36 6 3.5 4.5 23.3 cm
37 7 4.5 5.5 24.0 cm
38 7.5 5 6.5 24.6 cm
39 8–8.5 6 7 25.3 cm
40 9–9.5 7 7.5 25.9 cm
41 10–10.5 7.5 8.5 26.6 cm

Between sizes? Size up.