A queen-sized flat sheet is 90 inches by 102 inches. This sheet size is designed to fit over a queen-sized mattress, which typically measures around 60 inches by 80 inches. A flat sheet is generally slightly larger than the mattress it is placed over.
Compared to a queen-sized flat sheet, fitted sheets for a queen mattress are 30 inches by 22 inches shorter, measuring only 60 inches by 80 inches. A comforter for a queen-sized mattress typically measures 86 inches by 86 inches. Queen-sized comforters are also identified as full-sized and can be used either type of mattress. Knowing the size of a mattress is important to allow a perfect fit for any existing bed frame or trundle.