What is the right size or "Standard size" floating shelf?

We make shelves any size. The best depth dimension for you depends on the application.

 Ledges to display artwork are typically smaller like 3-6”

Living room or bedroom display shelves might be a bit more like 6-10+ inches. (most books are 9” or less)

Kitchen shelves are typically 12”. Nearly anything kitchen will fit on a 12” shelf (dinner plates are typically 11”)

In the kitchen It might be tempting to go bigger than 12” however I advise against doing so as will encroach into your countertop work space below.

 I always say less is more when it comes to open shelves. You want enough space to comfortably fit your items but not so much to leave a bunch of empty space in the back.