Hmmm, not sure, but if you mean what I would call 'upholstery' fabric (what you would use for cushions, curtains, sofa's etc) I would think that it is much thicker than typical quilting 100% cotton, and I would think that most of it would be man made fabrics. Sometimes it is 'treated' with fire-retardant chemicals?
I am totally supposing with this info, I guess it depends on the type and style of fabric you can find. I use some for cushion cover backs, found it difficult to work with (it didn't crease very well on the seams, and frayed quite a lot)
I wish it was as good as 100% cotton, as there is a rag market near me that sells nothing but home decor fabric, and it is CHEAP!