It’s a question almost every man has wondered at some point: When does the penis stop growing? The truth is, penile growth follows a natural timeline that’s tied closely to puberty. Most men reach their full size between their late teens and early twenties. Beyond that, the body’s development slows down, and hormonal changes stabilize, marking the end of penile growth.

However, that doesn’t mean growth and improvement are impossible later in life.

At Genesis Lifestyle Medicine, we understand that size, confidence, and sexual function are deeply connected to overall well-being. That’s why we offer P-Long®, a non-surgical protocol that aims to safely enhance length, girth, and performance long after puberty ends.

In this article, you’ll learn when growth typically stops, what influences penile size, and how the P-Long program can help you achieve lasting, natural results.

What is the “normal” penis size?

Before we discuss when penile growth ends, it helps to know what’s considered normal. According to multiple peer-reviewed studies, the average erect penis measures:

• Length: 5.1 to 5.5 inches
• Girth (circumference): 4.5 inches

That said, there’s a wide range of what’s normal: anything between 4 to 7 inches in length can be considered typical. Genetics, body composition, and even measuring techniques all influence these numbers. Remember, size alone doesn’t define masculinity or sexual fulfillment; performance, intimacy, and self-assurance play a much larger role.

When does penile growth stop?

Penile growth occurs during puberty, which is driven by the surge of testosterone, the key male sex hormone responsible for developing reproductive organs and secondary sexual traits.

• Early puberty (9-14): Testicular enlargement begins, signaling the onset of hormonal activity.
• Mid-teens (13-17): Rapid penile elongation occurs, followed by an increase in girth.
• Late teens to early twenties: Growth slows down and typically plateaus by 16-21.

By your early twenties, your body has reached its adult hormonal balance. Testosterone stabilizes, growth plates close, and penile development naturally stops. After this stage, no further natural increase in size occurs, although sexual function, erection quality, and appearance can still change depending on health, hormones, and lifestyle.

Factors that determine the length/girth of the penis

Hormonal balance

Testosterone plays the most critical role in penile growth. Low testosterone levels during puberty, known as hypogonadism, can delay or limit development. Without adequate hormonal stimulation, tissues responsible for elongation and vascular expansion may not fully mature. Maintaining healthy testosterone levels ensures optimal development.

Genetics

Your DNA largely dictates your body structure, including the overall length and girth of the penis. If men in your family share similar physical traits, genetics may be the reason. While genetics set the foundation, environmental and lifestyle factors can influence how those genes express themselves, especially during developmental years.

Nutrition

Growth depends on what you eat. Adequate protein, healthy fats, zinc, vitamin D, and B vitamins supports testosterone production and tissue repair. Conversely, malnutrition or restrictive diets during adolescence can hinder natural development and hormonal output.

Overall health during puberty

Chronic illnesses, endocrine disorders, or delayed puberty can interfere with the ability to produce hormones. Conditions such as pituitary gland dysfunction or thyroid imbalances can impact growth trajectories. Early treatment is essential for normal development.

Circulatory health

Penile tissue is highly vascular: it depends on strong blood flow for both growth and function. Poor circulation, sedentary habits, or smoking can negatively affect blood vessel development. Optimizing cardiovascular wellness can improve long-term penile vitality.

When to consider P-Long for penile enlargement

If you’ve reached adulthood and believe your penis has never fully developed or you simply wish to enhance your performance, P-Long may be the ideal solution.

P-Long is a non-surgical, evidence-based protocol created by urologist Dr. Judson Brandeis. It combines regenerative medicine, mechanical therapy, and vascular support to help men safely improve length, girth, and erectile quality over time.

The P-Long program typically includes:

• Platelet-rich plasma (PRP) therapy to stimulate cellular regeneration and blood flow
• Traction therapy using devices like RestoreX® to gradually promote tissue elongation
• Vacuum therapy to improve circulation and expansion capacity
• Nitric oxide supplements to support vascular health and tissue recovery

Together, these components work synergistically to enhance the body’s natural regenerative processes, all without surgery, fillers, or implants. Below, we describe a few situations when you may consider the P-Long Protocol to enhance penis size or girth.

You feel self-conscious about your size or proportions

If you’ve always felt that your size limits your confidence, P-Long offers a clinically guided way to address those concerns without the risks of surgery. By promoting natural tissue regeneration, P-Long helps you feel more balanced and self-assured.

You have mild erectile dysfunction or poor blood flow

Many men consider P-Long not only for size enhancement but also for improved erectile performance. The PRP and vascular therapies in the protocol can rejuvenate blood vessels, improving firmness, sensitivity, and stamina.

You want to avoid surgery or fillers

Traditional enlargement surgeries can involve significant risks, including scarring, infection, or unnatural results. P-Long is completely non-invasive and is formulated to stimulate your body’s own mechanisms for natural enhancement.

You want measurable results

Preliminary studies show that men who complete the full six-month P-Long program may experience average increases of 0.8 inches in length and 0.5 inches in girth. These results vary by individual but are backed by peer-reviewed data and real-world outcomes.

You’re committed to consistency

P-Long isn’t a quick fix: it’s a structured, progressive program that rewards consistency. Men who adhere to daily traction and vacuum therapy, attend scheduled PRP sessions, and maintain overall health see the best, most sustainable outcomes.

How much penile enlargement can I expect from P-Long?

While every man’s physiology is different, clinical studies and real-world experiences suggest that participants can see:

• Length gains: approximately 0.5-1.0 inches
• Girth gains: around 0.3-0.6 inches

Results typically become noticeable after a few months of consistent therapy, with optimal changes appearing after about six months. P-Long doesn’t just focus on size: it enhances erectile quality, sensitivity, and sexual confidence by improving vascular and tissue health.

At Genesis Lifestyle Medicine, we believe in helping you feel your best from the inside out and empowering you to achieve results that are as real as they are rewarding. Schedule a consultation today to discover how P-Long can help you reach your full potential.