The type of closet you have is very important when choosing the depth of your closet organizer.
Recommended Shelf Depth: 12 inches for 26 inch deep closets or less
Recommended Shelf Depth: 16 inches for 28 inch deep closets or more
The most common reach-in closet is a 24 inch deep closet with a header. The header is the area between the top of the closet door and the ceiling. Unless your closet uses tall doors or doors that go all the way to the ceiling, a 12 inch shelf depth is recommended. The reason is because of the space between the header and the top shelf in the closet.
In standard construction, the bottom of a header is typically positioned at 72 inches from the floor. The top shelf in a closet is typically placed at 84 inches from the floor. If you use a 16 inch shelf depth you will only have 8 inches of open space between the front of the top shelf and the closet header. You will only be able to place items on the top shelf that will fit between that space. When using a 12 inch shelf depth you will have 1 foot of access space allowing for larger items t be organized.
Recommended Shelf Depth: 16 inches
Typically you want to use the largest shelf depth for walk-in closet types. This will give you the most space for shelf storage. Deeper shelf depths also allow for more accessory choices because of the overall size.
There is a misconception that smaller walk in closets require smaller shelf depths, but that is not necessarily true. Whether you choose a 12 inch or 16 inch shelf depth, your garment bar is still going to be in the same position. 12 inches off the back wall. This means the hanging clothes will not move just because your shelf depth does. The used space is the same. A 16 inch deep shelf depth will provide more storage space in tighter areas however using a 12 inch deep shelf depth will give the appearance and feeling of more space.