I wear a 9 N shoe,ordered the 8-9 size, and it is a great fit.  (Could be a little snug for someone with a 9 wide foot.)  I had looked at slipper/booties in a dept store and the footbed was hard as a rock.  These Acorns are very soft-nicely padded.  Very warm also with a sole that lets me walk outside to get the paper every morning with no problems. Just the perfect warm,comfy slipper/boot.  What a deal!