At What Age Does Penis Growth Begin?

Penis growth is influenced by hormones in puberty. As such, the penis begins to grow more rapidly between ages 10 and 14 and can continue to grow until ages 16 to 21.

Many young men become concerned or self-conscious about penis size during adolescence, but then reach a completely normal penis size by the late teen years.

This article discusses when most penis growth takes place, what penis size is considered "normal," and how penis size is measured. It also covers several myths about penis size that young men should know.


Puberty is a time when young men experience physical changes, like becoming more muscular and getting taller. It's also a time when your penis may become erect when sexually aroused, during sleep, or when you're not expecting it. In addition, your testicles begin to grow larger and pubic hairs emerge.

The most rapid growth occurs between the ages of 12 and 16. The penis grows in length first and then begins to grow in girth (width).

You may notice that your penis size changes suddenly and fast. Your body, including your penis, may go through rapid changes for a few weeks, and then stay the same for months before changes begin again.

You will reach your fully developed penis size between the ages of 18 and 21.

Normal Penis Size

In general, your penis may continue to grow for one or two years after you stop growing in height, or four to six years after your testicles enlarge. It's important to know, however, that starting puberty later or earlier is not in any way related to your eventual penis size.

A flaccid penis is much smaller than an erect one, of course. If you are curious about how you compare, you can learn to accurately measure your penis.

The average erect penis is a little over 5 inches long and 4.5 inches around.

How to Measure a Penis
 Verywell / JR Bee

If you can urinate and engage in sexual activity (even of the solo kind) without any problems, you should not worry.


There are myths about penis size that young men may hear or share among friends that can make each other worry.

  • Erection ability: The size of your flaccid penis doesn't reflect the size of your erect penis. In many cases, a relatively small flaccid penis can become quite large when erect.
  • Sexual satisfaction: Studies have shown that penis size doesn't actually matter when it comes to sexual satisfaction of either partner.
  • Link between penis size and other body parts: The size of a man's penis is not related to the size or development of other body parts, such as hands, feet, facial hair, or baldness. There is no external or obvious sign that can be used to predict penis size or function.
  • "Manliness": Penis size is in no way related to one's physical abilities, personality traits, or masculinity.


A young adult man's penis grows most rapidly during puberty, especially between the ages of 12 to 16. Some young men might experience growth spurts, when physical changes in their height, muscles, penis size, and pubic hair change suddenly and fast.

Young adult men should know that the size of their penis doesn't say anything about how well it works during sex or how manly they are. If your penis functions properly without any pain, then there's no need to be concerned about its size.

A Word From Verywell

It's not uncommon to feel some anxiety about penis size, particularly during adolescence. But these concerns are usually centered around the above myths.

As you process the facts and become more confident in yourself, concern about your penis is more likely to become a thing of the past. If you still wish to have a larger penis, it's worth getting all the facts about penile enlargement treatments before moving ahead with any of them.

Frequently Asked Questions

  • When do boys start getting pubic hair?

    This usually occurs around the same age that a boy’s testicles and penis begin to grow, which starts anytime between ages 10 and 14. However, different hormones control pubic hair growth than those that control penile and testicular growth. So hair may develop before or after the sex organs start to change.

  • How much does a boy’s penis grow during puberty?

    It varies from person to person. In a study of 6,200 boys, researchers found that the average penis size increased 4.17 cm (about 1.6 inches) from age 10 to 16. That might give you a general idea of average growth, but individual growth may be very different.

  • Why do boys get erections during puberty?

    Erections can happen before puberty, but they become more frequent during puberty. At this stage, boys may experience erections for no reason. The penis fills with blood and stiffens. This can happen during the day or at night while sleeping. 

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5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Mautz BS, Wong BB, Peters RA, Jennions MD. Penis size interacts with body shape and height to influence male attractiveness. Proc Natl Acad Sci USA. 2013;110(17):6925-30. doi:10.1073/pnas.1219361110

  2. Prause N, Park J, Leung S, Miller G. Women's preferences for penis size: A new research method using selection among 3D models. PLoS ONE. 2015 Sep;10(9):1-17. doi:10.1371/journal.pone.0133079

  3. Klein DA, Emerick JE, Sylvester J, Vogt KS. Disorders of puberty: an approach to diagnosis and management. AFP. 2017;96(9):590-599.

  4. Tomova A, Deepinder F, Robeva R, Lalabonova H, Kumanov P, Agarwal A. Growth and development of male external genitalia: a cross-sectional study of 6200 males aged 0 to 19 years. Arch Pediatr Adolesc Med. 2010;164(12). doi:10.1001/archpediatrics.2010.223

  5. Cleveland Clinic. Erection ejaculation: How it occurs.