When I go out to the male clinic, I often have young men who feel that their penises are short and come to see me. So, what is the normal length of the penis and how do you measure it? There are usually two methods of measurement: one is to measure the weak state, and the other is to measure the change in the erect state. Measurement of room temperature is appropriate about 25 ° C, the penis weak length measurement —— with the hand to lift the penis flat, with one end of the hard ruler slightly hard against the pubic symphysis, as far as possible to compress the subcutaneous fat layer, the other end of the penis glans urethral orifice as the reference, the number read out that is the length of the penis in the normal state. The circumference of the penis is then measured with a dipstick at the cadre of the penis 1 cm from the coronal rim. Erection length estimation of the penis —– Due to the patient’s nervousness or discomfort with the office environment, they are mostly unable to get an erection in front of the doctor, so the length of the penis traction is commonly used instead of the erection length. There are numerous differences in human penis and body height, fatness, thinness, size of the features, etc., with different lengths and thicknesses. Large samples were investigated as follows: 1) Shi Chengli (1412 cases): penis weakness 4-14.5 (average 8.4) cm; erection 9-16 (12) cm, cm; circumference weakness 4.5-12 (8.3) cm, erection 8-14 (10.75) cm. 2) Liu Guozhen (1000 cases): penis weakness 4.9-8.6 ( 6.55)cm. 3)Wu Weicheng(2547 cases):The average length of penis in weakness was 7.43cm and the circumference was 8.17cm; the average length of penile retraction was 13.34cm, which was similar to the calculated erection length of 13.08cm, so the retraction length was considered to represent the length after erection. There are some differences in the measurement results of different people, and the results are also influenced by region and ethnicity. In addition, the length of the penis of the same person under normal conditions is not constant, such as tension, cold or severe fatigue can make the penis shorten. Therefore, it is difficult to judge whether the penis is normal simply from the length. We believe that the length of the penis is judged by whether it can complete normal sexual intercourse, and as long as it can complete the task of having children, it is normal, just like the sea cucumber that Dalian people often eat. Therefore, as long as the normal sexual intercourse can be completed, regardless of the length of the penis, it should be normal. So, what is really a small penis? If the penis is shorter than 2.5 cm before puberty and shorter than 5 cm after puberty, and if it is not developing normally and does not have erectile function, especially if the secondary sexual characteristics are poorly developed, sexually dysfunctional and unfertility and no sperm, then it can be considered as abnormal penis development.