Male 16 years old, penis length 20cm, thickness 5cm is normal. The average length of the penis of an adult male in China is (7.1±1.5) cm when it is soft, and it increases to (13.0±1.3) cm when it is erected, and the circumference increases from (7.8±0.7) cm to (12.2±1.2) cm. 16 years old male, the penis has been gradually developing and maturing, and it is a developmental normal with reference to the above standard. Penile development by race, region, genes, nutrition and other factors, the specific length varies from person to person, the above data is for reference only, such as the discovery of abnormal development of the penis or the feeling of obvious impact on the normal sex life, the need to consult a doctor in a timely manner. So male 16 years old, penis length 20cm, thick 5cm is normal, this age should adjust the mentality, focus on learning, do not worry too much.