Whether you sleep alone or with a partner, your mattress should allow you enough space to find a comfortable sleeping position. If you upgrade from a 4ft6 double mattress to a 5ft king size mattress, your mattress will be 6 inches wider and 3 inches longer, but this will give you a whopping 20% more sleeping space.
xSmall SingleSingleSmall DoubleDoubleKing SizeSuper King Size
2ft6 (75cm x 190cm)3ft (90cm x 190cm)4ft (120cm x 190cm)4ft6 (135cm x 190cm)5ft (150cm x 200cm)6ft (180cm x 200cm)
x3ft (90cm x 200cm)x4ft9 (140cm x 200cm)5ft3 (160cm x 200cm)6ft (180cm x 200cm)