I ordered a size up...In a closed shoe, I usually wear an 8 or an 8.5. In this shoe, I purchased a 9, which fit me perfectly. It has a roomy toe box so no pressure on a hammer toe!!!  It will accept an arch insert without making the shoe tight.  I require a shoe with a high arch...it's not that this shoe is lacking in any way.  This is my second pair of this exact style...other slightly different styles fit differently...mainly the toe box isn't as roomy.