This is very comfortable for sleep or casual/around the house wear.  No support for big breasts, but I could care less for casual use purpose. It's a "hanging out" top - not a sports bra. Another reviewer suggested two fixes for this: buy one size smaller  ... I did not try this yet, but I will.  OR wear TWO at once (this works pretty well, actually). The fabric breathes and is very, very flexible so that there is no binding.  I have three colors (nude, cream, black) ... someone said that BLACK dye causes fabrics to be a little tighter, and I do find this to be true with the black version of this top/bra. So, for more support, order your correct size in BLACK.  Oh, and as to size, this fabric is very, very stretchy, so you probably don't have to worry so much about getting the size exactly right. I ordered my t-shirt size, and it fit me perfectly.