Other than just warmth for the toes, an area rug under a bed defines the sleeping space within the decor scheme. Often the mood and style of the room, as well as its color scheme, is taken from the rug, so care is needed when selecting a rug for the bedroom.
An area rug placed under a bed should extend on either side of the bed at least 24 inches. Personal preferences may dictate a wider space, and laying small area rugs down beside the bed to determine which width is best for you is helpful.
If the bed is 60 inches (5 feet) wide, the rug should extend at least 2 feet on each side and should be placed horizontally, so the total length of the rug should be at least 9 feet. The standard for an area rug of this approximate size is 8-feet wide by 10-feet long. Using a standard size rug, it would extend on either side 2 1/2 feet and 18 inches at the foot. To place the rug correctly; see that it extends at the bottom the same length as on the sides; you'll have to place the rug under the bed 6 inches from the head.
If the design of the rug will not allow for horizontal placement -- and the width of the bed plus the rug measures 10 feet -- the length of the rug is a minimum of 9 feet. The standard rug length for a 10-foot wide rug would be 12 feet, and using a rug of this standard size would leave 5 1/2 feet extending past the foot of the bed. Placing a bench along the end of the bed will bring the rug and bed back into proportion.