Perhaps the best-known of all is the so-called stamp test. Buy a roll of inexpensive postage stamps. Before retiring for the night, moisten the stamps and apply them in a continuous ring around the mid-shaft of your penis. If you find upon awakening the next morning that the rings of stamps has been broken, it’s a clear sign that the penis achieved an erection during the night and that there is no serious damage to nerves or blood vessels serving the penis. If the ring of stamps is unbroken, it indicates that no nocturnal erection occurred, which is cause for further testing to see what physical impediments to an erection might be present.
Another self-test is the International Index of Erectile Function, or IIEF. The test consists of several questions, each of which can be answered with one of five or six multiple answers. The questions address recent sexual and erectile experience. Each of the multiple answers has a numerical value assigned to it. After answering all the questions, the numbers of your answers can be totaled to gauge your level of erectile function.