All shoes fit the same when measured in inches on the insole. European sizes vary a great deal between Italy, Germany and France. Take a Prada, Ferragamo, Dansko, Birkenstock or Finn Comfort shoe. They will all have different EUR sizes, but the insole measurement in centimeters will provide the true measurement. The basic rule of 31+ US womens size=EUR size is not entirely correct (34 + US men's). It mostly works for the middle of the bell curve.
This formula works: measure the insole length in centimeters (cm). One comes up with 26.5 (or measure in inches and convert it using Google to centimeters). 26.5 cm = 10 3/8" Add the two numbers to the left of the decimal point together (in this case 2+6=8). Then add the decimal point and the fraction to the left (8+.5=8.5). Voila, the US MENS size. For women's, you add one (8.5 Men's=9.5 US women's). For UK (unisexual) you subtract 1 from US men's (7.5 UK=8.5 US men's=9.5 US women's).
I sincerely hope this helps.