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Is Penis Size Genetic? What Science Says About Penis Size

11 min read
Is Penis Size Genetic? What Science Says About Penis Size

Concerns about penis size are extremely common among men - with only 55% of men satisfied with their penis size worldwide. As such, it's not uncommon to find yourself wondering why your penis is the size and shape it is.

Since so many health factors and physical characteristics are dictated by our genes, you're also right to wonder if penis size is also something that's passed down to us from our parents.

Here, we'll take a detailed look at the science of penis growth - including how much genetics play a part, how other factors contribute to size, and whether or not you can increase the size of your penis when you're fully grown.

Is Penis Size Genetic?

Yes, penis size is genetic. However, it's not just as simple as whether or not your father or other male relatives have big, small, wide, or narrow penises. In fact, there are a number of genetic factors and some additional factors that play a role in how big your penis becomes.

They include:

  • The presence of the SRY gene during early development
  • The effectiveness of the AR gene
  • The right balance of hormones
  • Nutrition through development stages
  • Environmental factors that impact hormones

What Genes Impact Penis Size the Most?

Scientists have proved that there are 4 main gene types at play when it comes to the formation of the penis and the organ's growth.

To understand how each of these genes impacts erect and flaccid penis length, it's worth taking a look at each in detail.

SRY Gene

Diagram of The SRY Gene The Male Determining Factor


At the most basic level, the SRY (Sex-determining Region Y) gene impacts penis size because it plays the most significant role in deciding whether you'll develop a penis or not.

As part of the overall 'male' Y chromosome, the SYR gene kick-starts the development of the testes in a male fetus.

Typically, female fetuses are identified as having two X chromosomes, whereas male fetuses have both an X chromosome and a Y chromosome. As part of the overall 'male' Y chromosome, the SYR gene kick-starts the development of the testes in a male fetus. In turn, the testicles produce male sex hormones (androgens) during the development of the fetus - and it's these androgens that are responsible for the whole male reproductive system developing.

AR Gene

Diagram of the Activation of Androgen Regulated Genes

The AR (Androgen Receptor) gene plays a more significant role in penis size than the SRY gene. In effect, the AR gene is like a messenger that tells the body how to respond to the male hormones that a responsible for making male features - including the size of the penis.

The AR gene doesn't directly make the penis bigger or smaller; instead, it affects how well the body listens to the hormones that do.

The influence of the AR gene starts very early in a fetus's development - sending instructions to the body about how to react to male growth hormones. The effectiveness of the AR gene varies from person to person - but if it's very effective, it can lead to a larger penis size. If the AR gene is less effective, it may lead to a smaller penis.

The AR gene doesn't directly make the penis bigger or smaller; instead, it affects how well the body listens to the hormones that do.

SHH (Sonic Hedgehog) Pathway

Diagram of the Hedgehog Signaling Pathway

You probably weren't expecting to see Sonic the Hedgehog mentioned in a discussion about penis-size genetics - but you haven't misread. The quirkily-named Sonic Hedgehog (SHH) gene was found to be involved in the regulation of organ growth - including the development of the penis.

The SHH signally pathway influences the early stages of penis development and urethral formation - and disruptions to this pathway can result in abnormalities or reduced growth.

HOXA and HOXD Gene Clusters

Diagram of the Homology between Hox genes in mice and humans

Image Source: Lumen Learning

HOXA and HOXD genes
also play an important role in the development of both the limbs and the genitals in fetuses.

Like the other genes we've talked about, variations in these genes could potentially influence the development of the external genitalia, including the penis, by affecting the growth of these organs and the way they're formed.

What Other Factors Impact Penis Size?

After seeing lots of evidence to suggest penis size is genetic, you might assume that beyond genes, there's nothing that's going to affect the size you have - but this isn't strictly true.

In fact, there are some additional factors at play - including:

  • Hormones
  • Nutrition
  • Environment

Let's take a look at each in some detail.

1. Hormones

Remember the AR gene we mentioned previously and its role in telling the body how to respond to the male hormones that influence penis size? Well, the main hormones it deals with in this regard are testosterone and Dihydrotestosterone (DHT).

Testosterone is the primary male sex hormone - and it's critical for the development of the penis and the other parts of the male reproductive system. During the development of the fetus, it mainly focuses on the different parts of the reproductive system developing - but in puberty; testosterone levels surge - driving more significant growth, including of the penis.

While testosterone has an effect on many different parts of growth in a male body, DHT is more focused on sexual development.

On the other hand, the impact of Dihydrotestosterone (DHT) on penis size is most significant while a baby is still in the womb. While testosterone has an effect on many different parts of growth in a male body, DHT is more focused on sexual development. During development, DHT ensures the sex organs mature properly - setting the stage for proper development later in puberty.

2. Nutrition

Nutrition plays an important role in the overall development of the human body - including the growth of the penis. Nutrition is especially important during the development of the fetus and later through puberty.

Nutrition isn't just about the number of calories required for the body to grow - it's also about consuming foods that create a positive hormone balance, maximizing the amount of testosterone and DHT, and how effectively those hormones can influence overall growth.

Of course, a developing fetus depends on its mother's nutrition while in the womb - so a pregnancy diet that includes essential nutrients, vitamins, and minerals will help a baby's sexual development. During puberty, rapid growth also requires that the individual consumes an adequate diet - including important nutrients like proteins, fats, vitamins (like vitamin D), and minerals (such as zinc).

Each of these has a positive impact on growth - including that of the penis.

All that said, nutrition doesn't change the predetermined size of the penis - that's down to genes. Instead, the right nutrient-packed diet will simply make sure nothing stands in the way of a person achieving the maximum physical development of the penis that's possible for them.


3. Environment

When talking about 'the environment', scientists consider a huge range of external factors - from chemical exposure through to lifestyle choices. Again, like nutrition, some of these factors are important during pregnancy, whereas others are important during puberty when it comes to penis development.

Since the body's response to hormones plays a big part in deciding penis size, environmental elements that interfere with hormone balance are important to consider here. Certain chemicals and pollutants are referred to as EDCs - or endocrine-disrupting chemicals. EDCs are found in some plastics, pesticides, and personal care products - and they can mimic, block, or otherwise interfere with the body's natural hormones, potentially affecting the development of the penis in the fetus and during puberty.

Of course, it's not just chemicals that play a part in hormone balance.

A person's fitness levels, the amount of sleep they get, and even stress levels can all affect hormone balance - so as well as avoiding EDCs, proper penis growth also requires a healthy lifestyle that includes adequate exercise, proper amounts of rest, and manageable stress levels.

What Factors Do Not Affect Size?

Now we've looked at the various factors that do play a part in penis size; we should also look at some that don't. There are lots of myths out there about what affects penis size - but many have been proven to be incorrect.

1. Race and penis size

It's commonly thought that people of certain races will have a larger-than-average erect penis length - but science says this is untrue. A 2014 study that explored penis length in over 1,600 men of different races in the U.S. found that there was less than 1cm variation in erect penile length and average penis circumference between all races and colors.

2. Masturbation and sexual activity and penis size

While conclusive studies on the effects of masturbation on penis size are limited, science again says no - with most urology professionals being confident that there is no link. Since masturbation doesn't affect penis growth, it's little surprise to discover that urologists don't believe any other type of sexual activity will affect penis size either.

3. Shoe size and penis size

"You know what they say about men with big feet" is a time-served suggestive comment about penis size - but science has proved that there's no link. In 2002, two urologists carried out a study involving men with foot sizes 8 through 13 - and the data collected showed no link between foot size and penis size.

4. Hand size and penis size

Like feet, large hands have often been considered an indication that someone will have a larger-than-average penis size. There are no studies to suggest this is true - but there are emerging theories that link finger-length ratios to penis size. This is unsurprising since the length of certain fingers is linked to testosterone levels in a fetus - so any hand/penis size correlation actually ties back to earlier points about the influence of hormones on penis size.

Can you Increase the Size of Your Penis?

Although you cannot change your genetics to increase penis size, Scientists have proven it is possible to increase the size of your penis without surgery. Positive scientific results have been found after the proper use of a penile extender and penis pumps.

Since we've discovered that penis size is most significantly influenced by genetics and the influence of those genes and conditions through fetus development and puberty, these factors cannot be changed when you're an adult. That said, this doesn't mean you're out of options when it comes to enhancing your penis.

There's a strong possibility that you can improve the look of your flaccid penis and the way your erect penis performs. Let's take a look at some of these methods.

Increasing the size of your flaccid penis

If you'd like to increase the size of your penis when it's soft, you may find some of the following techniques will help:

Trimming pubic hair Although not an actual increase in size, trimming the hair around your penis can make it look larger and can help with personal hygiene
Weight loss

Most people carry some excess body fat on the abdomen, which creates 'padding' around the penis. 

Changing your diet and losing a little weight can reduce this padding and make your penis more prominent - as well as help with heart and blood health.

Wearing a cock ring

Although penis rings are generally designed to help a person maintain an erection, they can also be used to keep a flaccid penis slightly engorged with blood, helping to make it look bigger than usual.

This is where it's useful to have a set of cock rings for different uses.

Using a penis pump or traction device As the studies linked above show, penis pumps, and traction devices can result in length and circumference gains, making the penis appear larger.

Of course, penis enlargement surgery is also something that people explore if they want to enhance their flaccid penis size. While often effective, this is a more extreme option than the methods we've discussed above.

Increasing your erect penis length

If you'd like to boost the length and circumference of your erect penis temporarily, you might find some of the following techniques useful:

 Using a penis pump

penis pump will help to draw blood into the penis using negative air or water pressure. This can make the penis more engorged with blood.

Using a cock ring will then keep this blood in the penis, helping it look and feel larger.

Using a traction device Over a period of time, proper use of a traction device is shown to increase the length of the penis, resulting in larger erections.
Using a cock ring Using a cock ring without a penis pump is also an effective way of trapping blood in the organ, assuming you have no ED issues that prevent you from getting hard.
Improving your health

Regular exercise, a balanced diet, and avoiding smoking and excessive alcohol can improve cardiovascular health, leading to better erections.

Improved blood flow can make the penis appear larger and firmer when erect.

Pelvic floor exercises Exercises, such as Kegels, can improve the firmness and strength of erections, making your penis look larger during sexual activity.

Are permanent gains possible?

Although there are lots of sources of information that claim all penis extension devices are ineffective, the International Society for Sexual Medicine studies linked above show that this is not true. Proper use of effective devices has been shown to offer permanent gains. What's more, there is a lot of anecdotal (i.e., not proven in lab conditions) evidence that can be found online that supports these studies.

Lots of people claim to have got permanent growth through the careful and repeated use of a penis pump or using a penis extender device.

It's important to note that no one suggests using a penis pump for permanent gains is a one-time thing - it's generally something that people say they have achieved after using a pumping routine over a series of months or longer.

Permanent gains are very firmly in the "results may vary" category. People who try to sell you something based on "guaranteed permanent results" or any other certainty are likely being dishonest. The truth is, there are too many variables to make any guarantees - and positive results will almost certainly require health and lifestyle adjustments for most men too.

Risks of trying to increase the size of your penis

While the techniques we've talked about above are considered safe when done according to the device manufacturer's guidelines, there are some techniques that could lead to temporary or lasting damage to your penis.

For example, overuse of a penis pump could lead to bruising or soreness - also the case if you use a cock ring that's not the right size. Likewise, most penis massaging techniques are also safe if done properly - but may lead to soreness and bruising if done excessively or with too much force.

It should also be said that there are countless sources of medications, creams, and supplements online that supposedly offer gains.

It's absolutely essential that you talk to a healthcare professional before taking any kind of medication or supplement that isn't prescribed - misuse of drugs, allergies, or undisclosed ingredients could be seriously harmful.

While it's understandable that many men would like their penis to look or be larger than it is, it's very important not to misuse products or techniques in an effort to get better gains or try to speed any processes up. You only get one penis - it's important to look after it!

In Penis Size Genetic? A Summary

Adult penile length is genetic. The genes you inherit from your parents will dictate whether you develop and penis - and then how that organ develops - both in the womb and then later in life during puberty.

Although your genes cannot be altered, there are a series of additional factors that play a part in making sure your penis grows as it should - including your hormone levels (and lifestyle factors that impact hormone levels), your health as you develop, and the amount of rest you get during growing phases.

Scientific studies have shown that it is possible to increase penis size in spite of your genetic make-up too.

Proper use of penis pumps and penile traction devices have been shown to offer gains when used over a period of time. Throughout life, penis and erection health also owes a lot to a healthy lifestyle - so plenty of exercise and rest is vital when making the most of what you've got - as is moderating the amount of smoking, drinking, and stress in your life. And, remember - science also tells us that penis size is much less of a consideration for partners than many men assume it is, so trying not to get hung up on size is also a great way to reduce anxiety and enjoy your sex life.

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