However, if you want an elaborately-designed bed frame, the size can be considerably wider and longer; depending on how elaborate the design is. For a standard King size bed in the United States, dimensions are at 76 inches in width by 80 inches in length; or approximately 198 centimeters wide by 203 centimeters long. For your King size bed frame with a very basic design, typical dimensions would be about 83 and ½ inches long and 82 and ¼ inches wide.