The length of the penis varies from person to person and usually, in adult men, the average length of the penis is 5cm to 6cm when it is not erect, while when it is erect, the average length of the penis is 11cm to 13cm. The main methods of penis measurement are: 1. Measurement of the natural flaccid state: respectively, in the upright position so that the penis and thighs at an angle of 60 °, 90 °, 120 °, on the dorsal side of the penis, measuring from the glans anterior end of the glans to the skin at the root of the penis and from the glans anterior end of the glans anterior end of the glans to the front of the pubic symphysis; 2. Measurement of erectile state of the penis: the measurer, after the patient’s penis is fully erected, makes the patient’s penis press down, so that the angle between the penis and the thighs reaches 90 °, at this time, measure the length from the front end of the head of the penis to the middle of the front of the pubic symphysis, that is, the length of the penis when it is erected. Usually, the normal range of the penis is: resting state length is greater than 4cm, the length after erection is greater than 7cm, but does not mean that the length of the penis is not in this range is not normal, as long as both spouses are satisfied with their sex life.