A lot of people have gone to buying a white or off -white bed cover then just using the quilt as a 'throw' for color, etc. that way it doesn't have to fit the mattress/springs exactly. I have made several quilts that were labeled as queen size. Only the American Beauty quilt by Marti Michel really fits our queen size bed perfectly. Our bed has the big box springs and ridiculously thick mattress. That bed is in one of our guest rooms. On our king size bed, we have an iComfort mattress and it is actually a thinner mattress. The quilt on it is a queen size but I had added several inches all the way around to use it on the queen size bed. It actually turned out way too big for the queen size bed and it is pretty skimpy on the king size. One of these days, I'm going to go the bed cover route and just use my quilts as accent pieces.

If possible, just measure the bed. Do you want just the top, hang down a little or reach the floor like a bedspread?

Well I see I said the exact same thing as everyone else. LOL

The queen sizes I make are mostly 90"X 102"

Don't forget to allow for shrinkage.