Is Penis Size Genetic?

Though genetics do affect penis size, several other important factors also play a role in determining the size of your member.

Dr. Jed Kaminetsky
Board Certified Urologist, expert in male sexual dysfunction
by Dr. Jed Kaminetsky Last updated 05/23/2022

Puzzle of DNA for penis size genetics

Ever wonder how you got the penis size that you did?

If you've measured, assessed, or assumed, you've probably come to one question: Is penis size genetic?

It’s a valid question. After all, genetics determine a lot about our physical characteristics, but is penis size one of them? 

Let’s see if you should be sending your dad a thank you card for what you got or if we’re about to open a family rift.

Quick FAQs

Yes and no. Genes determine whether or not you will be born male or female, but other factors can affect the size of the penis.

Things like hormones and nutrition can have an impact on penis size.

Studies show that the average penis size is 3.6 inches flaccid and 5.1 inches long while erect.

Studies show that men are far more concerned with the size of their penises than their female partners.

Is penis size genetic?

Ppenis size and genetics

Are penis sizes genetic? 

Short answer, yes, but not like you probably think.

Just because your parent had a smaller or bigger penis doesn't necessarily mean you’re destined to inherit that exact same size penis.

However, it is common for siblings to have similarities in the penis department, be it:

  • size or length
    • shape or bend
    • circumference or girth

      Several factors play a role in how big or small a penis becomes after puberty, including genetics. 

      Which genes affect penis size?

      The genes that affect the size of the penis

      Penis size is determined by a combination of several genes, specifically sex chromosomes.

      Sex chromosomes determine biological sex. 

      They also outline the sexual characteristics that begin to emerge sometime around the age of puberty, such as facial hair.

      Males and females have two sex chromosomes:

      • males are X and Y
      • females are X and X

      The Y chromosome is inherited from the father and contains the SRY gene, which is considered the "male-determining" gene.

      The SRY gene also sets the stage for the internal and external reproductive system formation, which, for males, is the testes and the penis.

      Even though that Y chromosome makes men biologically male and penis owners, it doesn't fully determine things like penis length or girth.

      Instead, these characteristics may have more to do with the 900 genes that the mother contributes through the X chromosome.

      By contrast, the Y chromosome only comes with about 90 genes.

      Even though genetic makeup comes directly from your parents, a person might also develop genes that are unique to them.

      And genetic mutations are perfectly possible as well.

      This means that the full characteristics of the penis, including its size, may or may not be wholly due to the genes contributed by parents.

      Every person on the planet has specific phenotypes—or traits—that are unique to them.

      For example, maybe a child’s nose is huge, but the parents both have perfectly pointed button noses. 

      This kind of variance can be related to something referred to as “de novo genes.”

      These genes are a bit like mutations—the gene changed somewhere along the line and is no longer like that of your parents.

      De novo gene development is still a bit ambiguous, but science has proven that they can determine specific physical traits, including penis size.

      Other factors that affect penis size

      Other factors that play a role in determining penis size

      As noted earlier, a whole host of factors will ultimately determine the size of a penis, not just genetics.

      Some factors can be environmental and not necessarily related to genetics at all. Below are two good examples.

      1. Hormones

      Testosterone and penis size

      From the time of fetal development, hormones begin to influence penis size.

      For example, naturally present androgens like testosterone can influence the size of the penis while a fetus is in development.

      Likewise, later in life, during puberty, testosterone and other growth hormones influence penile growth.

      This is why young boys diagnosed with micropenis may be treated with testosterone to encourage penis growth.

      However, hormonal exposure while the body is in development can also influence how the penis grows.

      Exposure to estrogens in the environment during puberty, which is a predominantly female sex hormone, may mean less penile growth.

      2. Nutrition

      Nutrition and penis size

      Nutrition, or lack thereof, can also affect the size of a penis.

      If a pregnant woman does not get the proper nutrition during pregnancy, it can affect the growth and development of the fetus, right down to reproductive development.

      Likewise, malnutrition during the early childhood years may affect your growth processes and lead to having a smaller penis.

      What is the average penis size?

      What is the average penis size?

      A PubMed Central study used a systematic review of up to 15,521 men and found that the average length is 3.5 inches soft and 5.1 inches when erect.

      Another study involving over 1,600 American men found the mean girth 4.8 inches while erect.

      More than 9 out of 10 men do have average-sized penises. Yet, many men think they're smaller than normal or wish they were better endowed.

      Popular penis size myths

      Myths about factors that affect penis size

      We've all heard the myths:

      • Well, if he's got big feet, then his penis is…
      • Make sure you check out the length of his fingers…
      • If he's [insert ethnicity here], then his penis is…

      The thing about these myths is that they are just that: myths.

      Here's a closer look at some of the most popular myths surrounding men and the size of their penis.

      1. Shoe size

      Myth that penis size is associated with shoe size

      Even though this is one of the more prevalent myths, there is no link between shoe size and penis size.

      There really is no correlation.

      2. Finger length size

      Myth that finger length is associated to penis size

      Just as a man with big feet may not necessarily have a bigger penis, a man with long fingers may not either.

      While we're on physical characteristics and penis size, you should also know that these are not related to penis size:

      • Height
      • Arm or leg length
      • General body shape
      • Weight

      3. Race and penis size

      Myth that skin color determines penis size

      This one gets a lot of attention too, and there may be some science to support this, but very little.

      A 2017 study conducted by the International Journal of Impotence Research did show there was about half a centimeter of difference between men with darker and lighter skin colors.

      More than size matters

      With all things considered, there is one key thing to remember when it comes to penis size. 

      When it comes to sexual partners of the opposite sex, 85 percent of women are perfectly pleased with their man's penis size.

      Percentage of men that are satisfied with their penis size vs what women think

      The more important factors are that a partner can work with what he's got.

      As an adage, remember that confidence is still ranked as one of the sexiest personality traits.

      Takeaways

      In the end, genetics do play a role in the overall size and shape of a penis, but the part played may not be as straightforward as expected.

      Penis size has a lot of determining factors, including:

      • genetics
      • environment
      • hormones and more

      The bottom line is size can matter but not as much as you think. 

      So, whether it's nature, genetics, parents, or sheer luck to blame, make the best of what you have.

      Sex is an enjoyable thing, and there is no reason to let misconceptions about the size of your penis get in the way.

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      Dr. Jed Kaminetsky

      Dr. Jed Kaminetsky

      Dr. Jed Kaminetsky M.D. is an American Board Certified Urologist and earned his Medical Degree at New York University. In his tenure he became a member of the American Urological Association and the American College of Surgeons. Dr. Kaminetsky pioneered the minimally invasive Rezum BPH treatment and is an expert in male and female dysfunction.

      Sources:

      Absorption Pharmaceuticals LLC (Promescent) has strict informational citing guidelines and relies on peer-reviewed studies, academic or research institutions, medical associations, and medical experts. We attempt to use primary sources and refrain from using tertiary references and only citing trustworthy sources. Each article is reviewed, written, and updated by Medical Professionals or authoritative Experts in a specific, related field of practice. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

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      The Content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

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