Generally speaking, it is normal for the penis to be more than 4cm when it is soft and more than 8cm when it is erect. Generally speaking, the length of the penis of a normal adult male is 4~8cm in the soft state and 8~15cm in the erect state.The male reproductive system develops later, and penis development usually starts from puberty until it stops at the age of 18. The penis usually stops developing around the age of 18 when a male reaches adulthood, but it may develop until around the age of 22 due to slower development in some men. If you have a short penis after the age of 18, you need to see a doctor for an examination and early treatment. Generally speaking, if you pay attention to maintaining good personal hygiene and paying attention to nutrition, there will be no problem with the development.