What Is the Average Penis Size for Boys and Teens?

Knowing When or When Not to Be Concerned

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Adolescence is a time for growth spurts and other changes spurred by the onset of puberty. For boys faced with these changes, it can be a time of great uncertainty as some will inevitably fall behind others in their development.

Among the key changes is the sexual maturation boys will undergo as the testicles get larger and the scrotum begins to thin and redden. In tandem with these changes is the growth of the penis which can develop at different rates for different boys.

As sexual awareness increases, concerns about penis size may deepen, particularly if all other signs of puberty (including height, body hair, and changes in voice) are robust. Knowing what to expect—and what an "average" penis size really means—can help alleviate a lot of the stress.

Normal Penis Development

The good news is that penis size is rarely a sign of a medical problem. With that being said, there are few answers about "normal" penis size that will satisfy an emotionally impatient teen.

Between the ages of 10 and 14, when most of the growth spurts occur, boys will often feel the need to "size up" with their peers, believing themselves to fall short if they are anything less than average. Even in boys as young as 11, the visible changes seen in others can quickly turn from a source of curiosity to one of anxiety.

To help dispel these fears, parents need to understand and share the facts about normal penis development with their sons if and when it becomes an issue.

Stages of Development

Generally speaking, a boy's genitals will develop in somewhat predictable stages. According to longitudinal research from the National Institute of Child Health and Human Development, the stages of sexual maturation in boys break down roughly as follows:

  • Onset of puberty: 9.5 to 14 years
  • First pubertal change: enlargement of the testicles
  • Penis growth: around one year after the testicles have started
  • Appearance of pubic hair: 13.5 years
  • Nocturnal emissions ("wet dreams"): 14 years
  • Facial hair, voice change, and acne: 15 years

What is important to note is that, unlike wet dreams and acne, there is no specific age by which the genitals will start to grow. In boys—even more so than girls—it can be difficult to know exactly when puberty will start and how it will develop.

For some, it may appear as an almost single event. In others, it may develop in fits and starts right through early high school. While boys in a family often follow similar growth patterns, there can even be variations among brothers that defy expectations.

Even if a penis appears small by the age of 14, there is still an opportunity for growth. With that being said, many parents will want to schedule an appointment with the family doctor if their son's penis hasn't started to grow after the appearance of body and facial hair.

Generally speaking, by the age of 18 to 19, little additional growth can be expected.

Average Penis Length by Age

The average penis length by age, outlined in Adolescent and Young Adult Health Care: A Practical Guide by Dr. Lawrence Neinstein, should only serve as a guideline for genital development in boys.

It should not be used to check if a boy is developing "on schedule" (an action that may only underscore a boy's insecurity). Rather, it should be used as a reference if your son fears he is falling behind in relation to all other markers for puberty.

The approximate ranges of a non-erect penis by age are as follows:

  • Age 10 to 11: 1.6 to 3.1 inches
  • Age 12: 2.0 to 4.0 inches
  • Age 13: 2.0 to 4.7 inches
  • Age 14: 2.4 to 5.5 inches
  • Age 15: 3.1 to 5.9 inches
  • Age 16: 3.9 to 5.9 inches
  • Age 17: 3.9 to 6.3 inches
  • Age 18: 4.3 to 6.7 inches

Because there may be errors in how the penis is measured, it is usually best to have the measurement done by a pediatrician or, better yet, an adolescent health specialist.

Diagnosis

The diagnosis of an abnormally small penis would seem to be a pretty straightforward process, but it is actually not. While a physical exam may establish that a boy's penis is below what might be expected for his age, it cannot accurately predict how much growth may still occur. This is especially true for boys 14 and under who may not yet have developed the secondary physical characteristics of puberty.

A physical exam may be more telling between the ages of 15 and 16 when the penis is most likely to experience growth. But even then, there may be factors other than growth that explain a penis' abnormally short appearance.

One such example is childhood obesity in which excessive pelvic fat obscures an otherwise normal-sized penis. The same may occur if a boy has a very large frame, creating the impression that the penis is smaller than it is.

Less commonly, there are congenital conditions that limit how much of the penis is externally seen. Examples include penoscrotal webbing (in which the scrotum extends up the underside of the penis, creating an indistinct junction between the two) and phimosis (in which the foreskin is unable to retract).

Micropenis, defined as a penis 2.5 deviations smaller than the mean average for the age, is an even less likely cause but can sometimes occur as a result of a genetic disorder (such as Klinefelter's syndrome) which impedes the production of testosterone during fetal development.

Micropenis

Treatment

Generally speaking, after the age of 8 there is little a doctor can do to promote penis growth in boys. For boys 8 and under, testosterone replacement therapy (TRT) may be used, but, even then, it is really most effective in toddlers 3 years and under.

If used early enough, TRT (delivered in three intramuscular injections over 12 weeks) may increase the child's penis size to the reference range for his age. After 8 years of age, TRT tends to be far less effective.

For older boys, surgery may be explored to treat concealed penis abnormalities. The approach can vary by case but may include circumcision or more extensive reconstructive procedures in which the skin of the penis is "degloved" and repositioned with sutures and skin grafts.

Penis enlargement surgery (phalloplasty) is not considered a reasonable option until later in life. The risk of complications may outweigh the perceived benefits, and the results tend to be variable at best.

A Word From Verywell

While concerns about penis size may be understandable in boys going through puberty, it is unhelpful for those emotions to be echoed or reinforced by parents or family members.

Ultimately, penis size should never be considered a measurement of one's manhood or virility. These cultural attitudes only serve to undermine a boy's confidence at a time when he is only just starting to explore who he is.

If your son comes to you concerned about his penis size, take the time to discuss his feelings without diminishing them. In some cases, penis size may only be a symptom of a larger problem. In some cases, there may have been teasing at school or an underlying lack of confidence for which penis size is emblematic.

Whether the issue is physical or psychological, it often helps to work with a medical professional trained in adolescent health. By allowing an objective third-party into the conversation, you can avoid any suggestion that there is a "problem" that needs resolving.

Acknowledge your son's feelings and reassure him of his self-worth, but avoid false assurances and platitudes that may only add to his anxiety.

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