When choosing a rug size for a king bed, a 9x12 rug is typically recommended as it provides enough space for the bed and complements the room's aesthetic. However, the size of the rug should also be determined by the dimensions of the room and the furniture placement. It's important to leave 10 to 20 inches of bare floor between the sides of the rug and the walls, and the rug should extend at least 18 inches beyond the sides of the bed. Other options include 8x10 and 6x9 rugs, but a 9x12 rug is considered the best fit for a king bed