King mattresses measure 76" x 80", providing the widest sleeping surface of any standard mattress and offering each sleeper approximately 38" of personal space. This popular size for master bedrooms accommodates most sleeping positions and provides excellent motion isolation for couples. Perfect for couples who want maximum room to spread out, families who co-sleep with children or pets, or individuals who prefer extra space, King mattresses require bedrooms at least 12' x 12'. Browse our entire selection of California King mattresses below.