This question is conclusive. If it is ordinary hiking shoes, especially all-leather, it must be one or two sizes larger. If you use double-layer boots at high altitude, because the outer layer is plastic, it will not shrink. Choose by normal size.
(1) Without tying the shoelaces, lean your foot on the heel and feel the support of the sole to the foot, especially whether there is a reasonable arc at the foot socket;
(2) Whether the left and right sides of the shoe are of appropriate size, there should not be too much space, and there should be a large space in front of the toes;
(3) Lean your foot towards the toe of the shoe, and there should be a gap between one and a half to two fingers between the root of the foot and the heel;
(4) Tighten the shoelaces, the roots, ankles, soles of the feet and other parts should be reasonably supported, and there should be no space or too tight feeling anywhere;
(5) Knock your toes vigorously on the hard ground. The toes should not touch the toes of the shoes. If they arrive, the shoes are still too small;
(6) The next choice is to shorten the running-in period of the fit as much as possible. After tightening the laces, the heels should not be too tight, the ankles of high-top shoes should not be too tight, and the tongue should not be too tight on the instep. In fact, as long as you choose the right size and good enough shoes, you may not need a break-in period.