When Does Your Penis Stop Growing?

For most people, the penis stops growing in the late teen years or early 20s. Once your penis has reached its adult size—which is largely determined by genetics—there is little you can do to change or increase the size of your penis. With that said, research suggests that around 95% of people with penises have an average penis size.

This article walks you through the timeline of penis growth, including the various factors that influence it, as well as appearance. It also explains when to see a healthcare provider if you don't think your penis is developing as it should.

A Timeline for Penis Growth

Most young people experience a slow and steady growth of the penis during childhood, beginning at birth. However, the most rapid growth of the penis happens during puberty, with the peak growth between the ages of 12 and 16.

Penises usually increase in length and girth at the same time. For most, the penis stops growing in the late teen years.

The testes follow a different growth curve. They remain the same size throughout childhood, even as the penis grows in length. At about the age of 8 to 9, they begin to grow, with the most rapid growth happening between the ages of 11 and 15.

For a more personalized answer about when your penis will stop growing, consider your puberty timeline. The penis usually stops growing four to six years after you experience enlargement of your testicles. That means that for most, the penis is fully grown between the ages of 18 and 21.

Factors That Influence Penis Growth

Most of the variations in penis size can be attributed to genetics. Just like your genetics play a role in how tall you are, they affect length and girth of the penis. 

However, as with most physical characteristics, environmental factors also play a role:

• Hormones, particularly testosterone, affect how much your penis grows during puberty. People with lower levels of testosterone may have smaller penises for that reason. Testosterone can be raised naturally by a healthy diet and exercise, and they are related to erectile function as well.
• Chemicals that affect hormone levels, known as endocrine disruptors, may affect penis size. In particular, chemicals called perfluoroalkyl compounds (PFCs) have been shown to be associated with smaller penis size because they affect testosterone levels in the body. Females who are exposed to PFCs may have children who have shorter penises. 

Can You Increase the Size of Your Penis?

Some lifestyle choices can affect how big your penis looks. People who are overweight or obese might have part of their penis shaft buried or hidden beneath a layer of fat. This can lead to the appearance of a shorter penis. However, weight loss that leads to less fat around the base of the penis can give it the appearance of being longer.

Having abundant pubic hair can also obstruct the base of the penis and make it look shorter. Trimming or removing pubic hair can help the penis appear longer. 

Although numerous over-the-counter pills, supplements, creams, weights, or exercises claim to increase penis size, there is not enough scientific evidence to verify they work.

There are medical and surgical interventions that may increase penis size but the scientific evidence is very limited. These interventions require expert medical or surgical care performed by a highly-trained and skilled urologist:

• Autologous fat injection: An injection of a person’s own fat into the penis
• Fillers: Four to six injections of fillers such as hyaluronic acid
• Grafting procedures: Uses artificial or your own skin or fat 
• Biodegradable scaffolds: Injection of re-absorbable material that promotes new tissue growth 
• Penuma: A surgical silicone implant that works about 57% of the time

Does Penis Size Matter?

Research shows that nearly half of men are concerned about their penis size, or wish their penis was longer. Men also overestimate how long the average penis length is, which can add to insecurity. 

However, your penis is healthy if you don’t have issues with urination, sexual intercourse, or reproduction. Penis size is not an indicator of your testosterone levels, masculinity, reproduction ability, or sexual performance.

Other Body Changes During Puberty

The most rapid growth of the penis occurs between the ages of 12 and 16, which is when many other changes are happening as the result of puberty. Here’s what people who were assigned male at birth can expect during puberty. 

For many males, puberty begins at about age 11, with a growth spurt that is noticeable. During this time, you may also notice these changes:

• An increase in acne and body odor
• The development of pubic hair and other body hair
• Vocal changes and the deepening of the voice
• More frequent erections and nocturnal emissions (wet dreams)
• Mood swings

It’s also entirely normal for boys to experience breast growth, which can last as long as a year or two. This is part of the normal hormonal process that boys undergo during puberty, and it usually regulates on its own. 

When to See a Healthcare Provider

Puberty is a complex time, and it can be hard to know what’s normal and what might require some medical advice. When in doubt, it’s always a good idea to speak with a healthcare provider. You should reach out for medical advice if any of the following apply:

• Initial signs of puberty have not appeared by age 14.
• You have true concerns about the length of your penis. Most penises are within the variations of normal, but about 1.5 per 10,000 children in the United States. have a micropenis (a stretched, flaccid penis that is shorter than 3.66 inches).
• Your concerns over penis size are interfering with your quality of life or sexual function.

Summary

For most people, the penis stops growing in the late teen years or early 20s and is largely determined by genetics. Most people have a penis that measures 3.4 to 3.7 inches when flaccid, and the size and shape will remain the same throughout your life. 

There is very little research to support products or interventions to increase the size of your penis. If you are concerned about the size of your penis, speaking with a healthcare provider, including a sex therapist, may help you come to terms with this part of your body.