Here is the size chart for choosing your new flip-flops. The sizes are based on your regular EU shoe size, but to be completely sure, you can check the sole length.
When selecting flip-flops, it's important that your foot fits on the sole without the heel or toes hanging over the edge. The measurements in the chart indicate the total length of the sandal itself ("Sole length"). We therefore recommend choosing a size where the sole length is about 1-1.5 cm longer than your foot, giving a little room at both ends.