If you are unsure about what size to choose, you can use this Size chart. The chart is based on the length of the lasts used for production. It can be used only indicative as the best way to find the right fit is by trying a physical model. If you still order a wrong size, you can read "Terms and conditions" to find out how to proceed.
How to measure the length of your foot properly
1. Place the heel against a wall.
2. Measure from the wall to the tip of your longest toe.
Note - one foot is often longer than the other, so measure the longest foot. For children add 10 mm to the measured length, leaving room for small feet to grow.