A California King mattress is a large mattress size designed for taller individuals or those who prefer extra legroom. It measures 72 inches wide by 84 inches long, making it longer than a standard King mattress, which is 76 inches wide and 80 inches long. This extra length provides additional comfort for people over 6 feet tall. These mattresses are ideal for spacious bedrooms and often require larger bed frames and bedding. California King mattresses are available in various materials, including memory foam, latex, and innerspring, catering to different sleep preferences and needs.