Penis length is measured primarily from the root of the penis to the external urethral opening of the glans. The normal size of the male penis varies from person to person and there is no fixed standard. Generally speaking, the length of a normal adult male penis in a soft state is about 4.5cm~11.0cm, with an average length of 7.1±1.5cm; the length of an erected penis is about 10.7~16.5cm, with an average length of 13.0±1.3cm, and the diameter of the penis in a soft state is 1-2 cm, and that of an erected penis is 2-4 cm. There is no other reference for determining the size of the penis than the actual length measured with a ruler. Penis size is related to genetics and nutritional status. According to different reference guides, a normal adult male with an erection that is greater than 8 cm can also be considered in the normal range, which does not affect sexual life and is not a cause for concern or treatment at all. It is important to note that penis size is not the only measure of sexual ability. Sexual ability is affected by a variety of factors, including physical condition, psychological state, sexual experience and so on. Therefore, instead of focusing too much on penis size, you should focus on your physical and psychological health. There is no fixed standard for the normal size of the penis, and the above lengths are for reference only. If the erection length is within the normal range, there is no need to worry. Very small erection lengths, especially in minors, should be further examined in the hospital to rule out hormonal and chromosomal problems.