Runs true to size. I wear an 9M.  I purchased the red Maryy Janes and also the black.  They  fit perfect and feel comfortable with the strap which prevents gapping on the side of each shoe.  Also, the inner cushion comes out which allows me to replace with my orthodic if needed.
I highly recommend these flats, and I have tried other brands and styles of Mary Janes, and these fit the bill.