Shoe sizes according to manufacturers are quite different.  We measure them to assure accuracy.  I receive many questions regarding sizing for shoes.  The chart below is quite accurate, but the bottom-line is centimeters on the insole.  The general rule of thumb to convert US sizes to EUR sizes for women is 31 + The us size.  If you wear an 8, 31 + 8 = 39.  That does not work across all brands.  For men it is 34 + US size = EUR.  Close but not exact.  Here is a chart to guide you:

Shoe Sizes                                                           Women
USA/Canada__(CM)____Europe______U.K._______(USA)_______
|____8____|___15____|___25_____|_____7____|______________|
|____9____|___16____|___26_____|_____8____|______________|
|___10____|___17____|___27_____|_____9____|______________|
|___11____|___17.5 __|___28_____|____10____|______________|
|___12____|___18.5_ _|___29_____|____11____|______________|
|___13____|___19.5_ _|___30.5 ___|_____12___|______________|
|___13.5_ _|___20____|___31_____|____13____|______________|
|____1____|___20.5_ _|___32_____|____13.5 __|______________|
|____2____|___21____|____33____|_____1____|______________|
|____3____|___21.5_ _|___34_____|_____2____|______________|
|____4____|___22____|____35____|_____3____|______5_______|
|____4.5_ _|___22.5_ _|____36____|_____3.5 __|_____5.5 ______|
|____5____|___23____|____36.5 __|____4_____|_____6________|
|____5.5_ _|___23.5_ _|____37____|_____4.5 __|_____6.5 ______|
|____6____|___24____|____38____|____5_____|______7_______|
|____6.5_ _|___24.5_ _|____38.5 __|____5.5 ___|_____7.5 ______|
|____7____|___25____|____39____|____6_____|______8_______|
|____7.5_ _|___25.5_ _|____40____|____6.5 ___|_____8.5 ______|
|____8____|___26____|____40.5 __|____7_____|_____9________|
|____8.5__ |___26.5_ _|____41____|_____7.5 __|_____9.5 ______|
|____9____|___27____|____42____|____8_____|_____10_______|
|____9.5__ |___27.5_ _|____42.5_ _|____8.5 ___|______10.5 ____|
|___10 ___ |___28____|____43____|____9_____|______11______|
|___10.5__ |___28.5_ _|____44____|____9.5 ___|_____11.5 _____|
|___11____|___29____|____44.5 __|___10_____|_____12_______|
|___11.5 __|___29.5_ _|____45____|____10.5 __|______________|
|___12____|___30____|____45.5_ _|____11____|______________|
|___12.5   _|___30.5_ _|____46____|____11.5 __|______________|
|___13____|___31____|____47____|____12____|______________|
|___13.5 __|___31.5_ _|____47.5_   |____12.5 __|______________|
|___14____|___32____|____48____|____13____|______________|
|___14.5_ _|___32.5_ _|____48.5__ |____13.5 __|______________|
|___15____|___33___  |____49____|____14____|______________|
|___15.5_ _|___33.5_ _|____50____|____14.5 __|______________|
|___16____|___34____|____51____|____15____|______________|
|_________|_________|__________|__________|______________|
|_________|_________|__________|__________|______________|
|_________|_________|__________|__________|______________|

I hope you have found this helpful.  Please email with questions.  We measure the insole to insure accuracy.