One frustratingly common misconception that I run into at least once a week is the size difference between a California King and a regular (or Eastern) King mattress. A California King mattress is smaller than a regular King mattress. A California King is 72″ x 84″, while a standard King is 76″ x 80″; in other words, the California King is 4 inches longer, but also 4 inches narrower. That means a King mattress has more overall surface area and more space between the partners than a California King does. Despite this, I often hear people state that they think a California King is the larger size. It’s not. It’s smaller by most metrics.