Have you ever had that moment when you wake up in the morning and your duvet has fallen to the end of your duvet cover? It's because you may not have the right size duvet to fit your cover. Bedding sizes are made with the dimensions of the bed and mattress in mind. They vary around the world with different countries having their own standards of measurement.
It doesn't matter which you decide to purchase first, your duvet or your duvet cover. However it can be a daunting thought to know if your duvet will properly fit your comforter. Many companies sell bedding and the duvet, but may not tell you exactly what the dimensions are. If the dimensions aren't listed make sure to double check with a customer service specialist to get the right numbers. You'll want to make sure your duvet fits your cover correctly.
Typically your duvet should be filled with a comforter that allows plus or minus two inches in dimension. If you want a snugger fit then you should purchase a comforter that is bigger than your duvet cover by two inches in both dimensions. You must also keep in mind that once you wash your duvet cover there is a chance that it will shrink 3-5%. There should also be ties on the inside of the duvet cover that are meant to be tied to a loop on the comforter. Not every duvet cover has this and that makes for a not so pleasant clump of duvet at the bottom of your cover.
See a selection of duvet covers here.
See a selection of comforters here.