How old is this boy? Please estimate. thank you

In the statistics of penis size, according to different statisticians, there are the following groups of data: 1. Jiang Yu and others measured the static penis length of 470 teenagers and found that the penis length above 17 was 7.0-9.8 cm. 2. Zhu Huibin and others measured the static penis length of 900 men aged 25-35. The length is 6.9 (plus or minus1.4cm) and the diameter is 2.5 (plus or minus 0.4cm). The penis length during negative pressure passive erection is 1 1.6 (plus or minus 1.7cm) and the diameter is 3. 3. Zhang et al. investigated the penis length of 2029 adult males in China, with an average of 7.2 1 (plus or minus 2.59cm).

However, there is no uniform standard for the definition of penis in China. It used to be thought that the static penis length < 4 cm was a small penis. Now, according to the draft length of penis, the reference value of penis is considered as: newborn < < 2.5cm, adult < < 5.5cm.

Attachment: Static penis length-measure the length of penis weakness, that is, the distance from pubic symphysis (the accessible bone structure in the middle of the lower abdomen) to the external urethral orifice.

Draft length of penis-hold the crown groove of penis head with thumb and forefinger, pull the penis to fully stretch it, and then measure it by static length measurement.

As for the length of penis after erection, there are few such data in China. Because in the traditional medical concept, doctors are more concerned about whether the sexual organs are mature and have fertility. There is not enough data on the length of "secondary" penile erection. It is generally believed that penile erection at 10- 19 cm is normal. I hope to see more authoritative data in the future.