Arxus Size Chart provides you with an easy way to find your correct boot size.
To measure your foot in an exact measurement you need a sheet of paper and a 90 degree angled object (for example a book).
Stand on the sheet of paper then place the 90 degree object against your toes. Put a mark on the paper at the point where the object meets your toes. Repeat this procedure at the back of your foot.
Measure the distance between the two marks, then add 8mm to achieve a clearance between the foot and the inside of the boot.
Use the internal size column on the Arxus size chart to find your size.