That should be a good size for a baby quilt. I like extra fabric so I can test tension on the sides, and the other way, so there is no danger of the back or batting ending before the top, as I roll it. I don't quilt for others, just for myself, so I am pretty generous with the backs and batting, but nothing is wasted, I use the batting on rag quilts, and save the backing strips for scrappy quilts. I also make my top borders just a little wider than I want them finished, so I can square up my quilt nicely when I am done.