how large is a king size mattress
King Mattress. The king size mattress dimensions are 76 inches wide by approximately 80 inches long â about 18 inches wider than a queen. This is the closest a couple can come to having as much personal space (38 inches) as each would have on a twin bed.ometimes still called a double mattress, a full size mattress is 53 inches wide, which is just 15 inches wider than a twin size (single). That leaves each partner only 27 inches of personal space, or about the width of a crib.