1:Measuring your foot length Make sure you're on a flat surface.Trace the outline of your feet on a piece of paper. Keep your writing utensil as perpendicular as possible so you get the most exact measurements. Once your feet are traced.use a ruler to measure from your heel to the tip of your longest toe. 2.Then use this shoe size chart to convert the length of your feet to U.S shoe size. For example If you choose US8.5.We will send size EUR 40.It comes with 25.5cm insole length If you feet are fat.you may choose the bigger one Hope this will helpful for you. and please contact us freely if you have any problem in the size :) Size:36 37 38 39 40 41 Size info: 36=Insole Length 235mm 37=Insole Length 240mm 38=Insole Length 245mm 39=Insole Length 250mm 40=Insole Length 255mm 41=Insole Length 260mm