Queen size sheets are larger than those for a double bed mattress, so they can fully cover the mattress. However, their larger size may result in a loose fit.
Queen size beds are 60 inches wide and 80 inches long. Double beds, also called full size beds, are slightly smaller at 54 inches wide and 75 inches long.
A queen size flat sheet can fit on any smaller bed, since it can be tucked in. However, fitted sheets best fit the specific mattress size provided on the label. A queen size fitted sheet may fit too loosely on a double bed.