There is no authoritative information on how much erect penis length and girth is normal. It is generally believed that the erect length of adult male penis is 13.0±1.3cm, circumference is 12.2±1.2cm, the above data is for reference only, the specific situation varies from person to person. Because, due to the development of each person is different, so the specific data on the length of erect penis and circumference, can not be generalized, there are obvious individual differences. However, if the appearance of the penis is normal and the length is 2.5 standard deviations smaller than the average length, it is mostly considered to be a small penis in clinical practice. Men need to pay attention to the protection of the penis in daily life, if you suspect that the length and circumference of the penis is abnormal, you need to go to the hospital in a timely manner to clarify the specific causes.