Well... it's a mystery! And an annoying one. You really have to check the measurements of your duvet and the cover you're considering because it seems like there are no 'standard' sizes, even though they are labeled king, queen, etc., there seems to be variation.

Also... there IS a top and a bottom to a queen duvet... it's slightly wider than it is long (or the other way around, I forget) but you have to make sure you have it in the right way and that helps to fill the cover.

I have in the past used a king duvet inside a queen duvet cover, and that has solved a lot of the problem for me.

The other thing is, if your mattress is really thick often the queen duvet/cover isn't wide enough to cover the sides of the mattress. And the king is way too big. Frustrating.

Try the Company Store (online) they sell oversized comforters.

It's a king size bed and you're right both the duvet cover and the comforter were king size and one side was empty! Looked horrible! Going to try the online company store and see if that does it! Not fun!

http://www.thecompanystore.com/primaloft-deluxe-supersize-down-alternative-comforter/CV17-ps-F11.html?prefn1=shopCollection&start=3&cgid=comforters-down-alternative&prefv1=primaloft