With regard to penis size, sampling survey shows that the longest penis in China is 1 1 cm, the shortest penis is 3 cm, and the average penis is 6 cm. The maximum diameter is 4.0 cm, the minimum is 1.5 cm, and the average is 2.5cm；; During erection, the longest penis is 18 cm, the shortest is 8 cm, and the average penis is 12 cm. The penis is measured by pressing the pubic symphysis with a hard ruler (you can squeeze the fat of the pubic mound slightly) and then measuring the urethral orifice of the penis at the size of the hard ruler (remember to measure it from above), where the pubic symphysis is in the hard bone part below the pubic mound, and the pubic mound refers to the inverted triangular fat pad with pubic hair on the penis. Weakness, erection and weakness are all measured by pulling the penis. As for the circumference, use a soft ruler to measure it under the coronal groove of glans penis 1 cm. About your "penis is not erect at the age of 15 this year, and it is 8cm and 15cm after erection", if the measurement method is correct, this size is really large and strong. And 15 years old is still growing, and JJ will grow to about 25 years old, so it is very likely that it will reach 18 cm in the future. But don't worry, it won't hinder normal use. You know, in the first stage of sexual arousal, women's vagina expands very badly in order to accept objects of unknown size. After that, it will tighten again and gently wrap the incoming object. An ancient Greek scholar once said: "During sexual intercourse, the role of vagina is to tighten the contents. He is so natural that he can adapt to any size. When it is short, it will stand out, long retraction, fat expansion and thin contraction. " As for "the classmates around me are very small, sometimes they are embarrassed to go to the toilet and it is not convenient to take a shower." What should I do or how can I make my penis smaller? Why is my penis so big? " This is closely related to genetic factors and acquired nutritional intake. Everyone is different. Just put it down and treat it with a normal heart.