If you google "quilt sizes," you will find several sites that list not only quilt sizes, but also mattress sizes. However, I've found it most reliable just to measure the top of a given bed and decide how long I want it to hang over the sides, and how much room I want at the foot and the top (do I want to allow enough to "encase" pillows or just to lie flat?), and then go from there.
One such site gives the following information for queen sizes:
For quilts: usually between 88"-99" wide; length about the same. Queen mattresses are usually 60" x 80". But you would have to add to this significantly, if you wanted more overhang, possibly as much as 13" on each side.