Facets has a wide variety of shoes and sizes.  The shoes are classified by the type of doll they were made for. Although they were fitted on a specific doll, they often fit other dolls with similar feet.  For example, many shoes made for Tyler Wentworth may also fit Sybarites.  There is a fit guide (and often photos) in the shoe listings to indicate how well a shoe fits.  You can see definitions of the terms at the link below.

If your doll is not listed, you can see the general size of shoes here: Shoe Sizing and other information