The total square mileage of California is 163,695 square miles, including water. This makes California the third largest state in the country, only smaller in regards to Alaska and Texas.
Subtracting the water square mileage from the picture, California's actual land square mileage only comes in at 155,959 square miles, meaning that 7,735 square miles in California are purely water.
County sizes in California differ greatly, with the largest being San Bernardino County, coming in at 20,164 square miles. On the other side of the spectrum is San Francisco County, the smallest county in California at only 91 square miles.