The California king size mattress, also called a Western king, is the longest mattress that is commonly available. At 84 inches (213.4 cm) long, it is 4 inches (10.2 cm) longer than the Eastern king and is preferred by many people who are more than 6 feet (1.8 m) tall. Like an Eastern king, it typically comes with two twin box springs. For some people, the drawback of this mattress is that, at 72 inches (182.9 cm) wide, it is 4 inches (10.2 cm) more narrow than the Eastern king.
A California King size mattress is roomy in width for 2 adults and taller people may prefer the California King with its longer length. A California King is 12" wider than a Queen bed but adds 4" in length. The foundation of any King bed is made from pairing 2 Twin (36" x 84") bases together to form a King base. One of the main reasons this is done, is so the foundations can easily fit up stairs and into small doorways.