The chart above will give you a good idea of how the different CLOSETbay closet rods match up to each other and how much weight they can support. Keep in mind though, this doesn't represent a real world application. In the real world you wont be hanging all of your clothes from the very center of the rod, they'll be spread out over the entire span. Your closet rod will probably not be exactly 6 feet long either. The shorter the rod, the more weight it can hold before sagging; the longer the rod the less weight it will hold before sagging. Here are some recommendations for lengths and support:
Oval Rod: Over 4 feet long use a Center Support or rod & Shelf Support.
Round 1-1/16" Diameter Rod: Over 5 feet long use a Center Support or rod & Shelf Support.
Round 1-5/16" Diameter Rod: Over 6 feet long use a Center Support or rod & Shelf Support.
If you are concerned that you may have too much weight for your closet rod and span, you can always use more center supports to help carry the load. Clothing distribution is also a big factor in how your closet rod performs. Keeping heavy garments at the outside and lighter garments toward the center of the rod will help prevent sagging.
There are 3 materials used to make modern closet rods, steel, stainless steel, and aluminum.
Steel offers the advantages of strength and resilience. Resilience simply means that the metal "remembers" its original shape and when flexed will return to that original shape.
Stainless Steel performs in nearly the same way as normal steel with the exception that it is resistant to rust and corrosion.
Aluminum offers the advantages of strength, rigidity, and a lighter weight than steel. It also offers some resistance to corrosion in certain situations.