Just like any other type of bedding sold online, duvet covers come in all sizes, ranging from twin size to California king. A single duvet is approximately 53 inches x 78 inches approx, a double duvet 78 inches x 78 inches, and a King duvet is typically 90 inches x 86 inches.
If you will be buying a new duvet, we suggest you buy from the same brand as your duvet cover as dimensions can vary slightly from one brand to another.