how deep should closet shelving be?

I'm near the end of the renovation of my condo. Other than find floor trims that will go between the tile and new laminate flooring, all I have to do is install shelving (and rods) for the master bedroom closets.I'm going to install custom wood shelving. However, I'm trying to figure out how deep (or how wide?) the shelves are supposed to be? It's a regular closet (not a walk-in). The shelf that sits above the closet rod; how deep should that be (ie. from the wall to the face of the shelf)? via /r/DIY http://ift.tt/2tjAQlU