Size conversions are difficult because the units for measuring are different in each system, and every last and shoe pattern vary. English sizes are based on the barleycorn, and were introduced by Henry VII. A barleycorn is 1/3rd of an inch. European sizes are mostly based on the centimetre. American lasts are similar to English lasts, but sized differently. This is a long winded way of saying there is no direct correlation between systems.
There are accepted conversions, like 36 = 4, and 42 = 8, and then we convert as well as we can. You will be used to where your own size usually fits on these charts, and your first order should assume your normal size. Our lasts are elegant and slightly long, so if you tend towards a half size, please order down a size. This usually works. We offer size 3 and 9 in popular ladies shoes, and 6 and 12 on mens',