We strongly recommend that you take into consideration the length in centimeters of your larger foot when choosing the shoe size to order.
Sometimes the reference number is not accurate enough for choosing the right size and changes according to the different model types.
To get the correct size of your foot, use the larger of the two (typically the right), and measure from the heel to the longest toe (as shown in image). It can help to placing your foot on a piece of paper and mark the two ends (immediately behind the heel and at the end of the toe) and then measure with a normal ruler.