i hope someone can answer your question, all i can do is tell you how they fit me. i bought a size 12 (or euro 46) and wear normal dress socks (that's right) as a surprising number of hiking websites recommend if cold is not an issue. i take a size 12 to 12.5 in nike shoes, an 11 in cowboy boots, and normally a 12 in hiking boots when i wear dress socks (i live and hike in L.A.) so i'd say with thin dress socks these boots are totally true to size. IF i was going to wear them with thick hiking socks, i'd definitely go up a half size to 12.5 also, my actual foot is 11.5 inches...and again i took a size 12 in these for use with thin socks, i'd have gotten a 12.5 if i wore thick socks.
hope that helps.
According to our fit models this item is running true to size.