The mattress of a king-sized bed is 78 inches by 80 inches. Determining the dimensions for a king-sized bed depends on whether a short drop or a long drop is preferred. A short drop quilt measures 104 inches by 93 inches. A long drop measures 120 inches by 112 inches.
If the quilt will be used as a bedspread, the long drop measurement is used. This measurement allows for the quilt to drape down the sides and foot of the mattress. If the quilt is to be used underneath a comforter, the short drop is preferred because it is easier to tuck underneath the mattress edge.