Apart from both being hard, the iPhone 5S and an erect penis share another, more surprising quality: they are about the same length. The BJU International journal of urology just came out with the information that the average erect human penis is 13.12 centimeters, or 5.16 inches, which incidentally is approximately the same length as an iPhone 5S with an average-size case on it. Without a case, the 5S is 4.87 inches long. If you can't visualize this, we suggest busting out your phone or your ruler, because we have to admit, it's kind of . . . underwhelming when you look at it. We'll get back to you with our next study on penis width using objects we have lying around the office.