A king-size mattress comfortably accommodates two adults, according to the Better Sleep Council. This type of mattress also provides sufficient room for children and pets that may want to share the bed, notes The Bedding Experts.
A king-size mattress is 76 inches wide and 80 inches long, states the Better Sleep Council. This provides each adult with a sleep area comparable in width to that of a twin bed. Pushing two extra-long twin beds together can create a makeshift king-size bed, making this a flexible arrangement for a guest room.
While a king bed provides the most personal sleep space for couples, it is best to check room measurements before making a purchase, notes the Better Sleep Council. A king bed may be too big to fit in some bedrooms, or it may be difficult to move it through doorways and hallways.