If your comforter is labeled "queen," it will typically go into a queen duvet. However, comforters labeled "full" will also fit queen duvets under most circumstances. Comforters and duvets are both often labeled "full/queen" and will fit either size bed. If the comforter comes in both full and queen sizes, however, the queen size will be the best fit for a queen duvet.

On the Other: Check the Measurements

Look at the packaging for the duvet and the comforter you are considering putting together. If you don't have the packaging, measure the pieces individually. Is the comforter smaller than the duvet by several inches? If so, it will fit. You will want at least an inch or two of space in the duvet around the comforter to enable you to put it in and remove it easily. If the comforter is larger than the duvet, it will not fit. For reference, full-size comforters typically measure about 80 inches by 90 inches. Queen-size measurements are about 86 by 94 inches, and full/queen are about 88 by 88 inches. This will likely vary some from manufacturer to manufacturer.

Bottom Line

It's best to check the label on both the comforter and duvet. A queen comforter will almost always fit a queen-sized duvet, but it it also possible to use full and full/queen comforters in most queen-size duvets.

Source:

Bed Bath & Beyond.com: Sizing Up Your Bedroom