A regular king-sized American bed measures 76 inches by 80 inches. A California king mattress, a good choice for tall people, is four inches longer and four inches narrower than a regular king bed and measures 72 inches by 84 inches. Custom or Super kings are 80 inches wide.
Outside of the United States, what is called a king-sized bed differs considerably in dimensions from country to country. For example, in Japan a California king is even narrower than the American version, at only 47 inches, while in Continental Europe, the king bed width is 63 inches. Thailand and Singapore's versions of king beds measure 72 inches across; New Zealand's king bed is more generous than the Japanese, but still gives a sleeper a fairly narrow width of 65 inches.