I don't know why.  I've ordered size 8 tevas before and I do love the style of these sandals so I have three different colors.  However, after ordering that size 8 the first time, I always ordered a 9 for a little more room.  This time I ordered a 9 and it was as small or smaller than the size 8 I bought the first time.  I actually wear an 8 or 8.5 in most shoes, but my point is that all three of them have been incorrectly size and with no foreseeable accuracy.  Nevertheless, this particular style shoe is my all time favorite.  It's much more secure and cushioned than most flipflop type shoes and that is incredibly important to me.  They are so comfy I can't even really complain about the odd sizing because I still wear all three pairs.  And I assure you my next shoe purchase will be another pair of teva sandals.  I'm just baffled because I have no clue what size to order.  LOL