Although genetics can play a role in penis size, many other factors can also affect penis size, including hormones, nutrition, and diet. Factors such as height and shoe size do not affect or indicate penis size or shape.

Many males may have concerns about the size or appearance of their penis from time to time. Various factors contribute to penis size, including genetics, environment, hormones, obesity, and nutrition.

Some products may claim to increase penis size, but there is little evidence supporting these claims, and some may lead to adverse effects, such as erectile dysfunction or damage to the area.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Learn more.

three generations of males walking together who may all have a similar penis size because of geneticsShare on Pinterest
Genetics, hormones, nutrition, and diet can all affect penis size.

Genes are the building blocks that determine a living organism’s appearance and behavior. Humans inherit two copies of each gene, one from each parent. Multiple genes make up chromosomes.

Humans have 23 pairsTrusted Source of chromosomes. Of these, there are 22 autosomes and one set of sex chromosomes. A person’s sex chromosomes determine their biological sex and secondary sexual characteristics.

Males inherit one Y chromosome from their male parent and one X chromosome from their female parent. Females inherit two X chromosomes, one from each parent.

The Y chromosome carries genes that oversee the development of male genitalia and fertility. It determines the development of the penis and testes but not necessarily penis size or girth. These characteristics may be dependent on the X chromosome.

The X chromosome contains around 900 genesTrusted Source, whereas the Y chromosome only has about 50 to 60 genesTrusted Source. This difference may explain why penis size varies among siblings with the same biological parents.

Genetic mutations may also affect penis size and appearance, as well as other physical characteristics.

While quite rare, genetic conditions sometimes influence penis size, including Kallmann syndrome and Klinefelter syndromeTrusted Source.

Thus, penis size depends on a combination of a person’s parental genes, their own unique genes, and other external factors.

The following factors also affect penis size:

Hormones

Just as estrogen and progesterone affect female sexual characteristics, such as breasts, hips, and fat storage, male sex hormones, or androgens, contribute to testicular and penile growth.

During puberty, the pituitary gland produces moreTrusted Source luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH promotes testosterone production in the Leydig cells of the testicles, and FSH promotes sperm production.

Variations in testosterone levels during pregnancy may cause penile abnormalities. For example, the mother may not produce enough human chorionic gonadotrophin (hCG) hormone, which stimulates testosterone development in the fetus.

Rare conditions, such as 5 alpha reductase deficiencyTrusted Source and congenital adrenal hyperplasiaTrusted Source, also affect testosterone levels and may affect genital appearance.

Even when testosterone levels are typical, some medical conditions may stop a person’s body from responding to testosterone correctly. This response is called androgen insensitivity syndromeTrusted Source.

When any of these hormonal issues arise, the penis of a male fetus may not develop in the usual way.

It is worth noting that these factors will only affect penis size and any genital abnormalities when a fetus is still in a uterus as the penis and other external genitalia are developing.

They will not affect penis size in males after birth, particularly not as an adult. For example, an adult male cannot enlarge his penis by avoiding endocrine disruptors.

Environment

Environmental pollutants, such as pesticides, plasticizers, and other chemicals, may have a negative effect on penis size. These chemicals may act as endocrine disruptorsTrusted Source and affect gene and hormone expression.

Epigenetics is a growing area of science investigatingTrusted Source how certain behaviors and environmental factors may affect gene expression.

ResearchersTrusted Source believe epigenetics plays a role in development and disease. They suspect it may influence hormone function and have a role in hormone disorders.

Research in a 2022 systematic review suggests that exposure to endocrine-disrupting chemicals before or after birth may affect puberty onset, including genital development.

A 2019 study also suggests that epigenetic-associated dietary influences may slow genital progression in adolescent boys.

Nutrition

Malnutrition in the womb and throughout life may affect hormones, growth, and development. Inadequate nutrition in adolescence can delayTrusted Source puberty.

While individuals undergoing delayed puberty typically catch up eventually, symptoms of delayed puberty may include a smaller penis and testicles.

Other factors

Genetics are the strongest predictors of penis size. However, factors such as body fat and the presence or absence of pubic hair may make the penis appear larger or smaller without affecting its true size.

For example, if someone has obesity, the penis may be “buried” in the prepubertal fat pad. This may give the appearance of a smaller penis when it is actually an average size.

When exposed to cold temperatures, the blood vessels in the penis constrict. This physiological reaction causes the penis to shrink temporarily.

Numerous myths about what factors determine penis size often lead to unnecessary stress and anxiety in people of all genders and ages.

A 2023 retrospective study of 1,160 people highlights a potential correlation between nose size and penis circumference and stretched penile length.

However, the researchers highlight that, despite the interesting correlation, the study involves a limited sample, and the findings have limited clinical significance. It also only highlights a potential pattern and does not explain a causative relationship.

There is no scientific evidence that suggests the following factors affect penis size or appearance:

The penis grows gradually after birth. However, the most significantTrusted Source growth occurs during puberty.

Puberty usually begins in males between 9 and 14 years of ageTrusted Source and lasts up to four years.

A 2020 review suggests that the average length of an erect penis is between 5.1 and 5.5 inches (in)Trusted Source. However, the author notes that volunteer bias may affect these results, suggesting that the most accurate average may be at the lower end of this range.

A 2023 systematic review of 75 studies involving 55,761 males analyzed the worldwide average penis length. The authors highlight the following mean average estimates:

  • 8.70 centimeters (cm) or 3.4 in when flaccid
  • 12.93 cm or 5.09 in when stretched in a flaccid state
  • 13.93 cm or 5.4 in when erect

The review involved studies published between 1992 and 2021 and suggests that average penile lengths increased in this period. The authors highlight the need for further research to confirm this trend.

The authors also highlight limitations and variations in reporting stretched penis lengths, suggesting that estimates may be inaccurate compared to erect lengths, which were more consistent.

A 2021 study involving a limited sample of 4,685 males in Italy suggests that the average flaccid penis circumference was 9.59 cm or 3.08 in. The average erect penis circumference was 12.03 cm or 3.82 in.

The penis enlargement or male enhancement industry claims that various enlargement procedures, vacuum devices, pills, and creams can increase penis size. However, there is limited research on many of these methods, and they may have serious risks.

A 2020 studyTrusted Source suggests that the majority of people seeking penis enlargement have average-sized penises, meaning that they are of adequate size for sexual activity and urination.

The Urology Care Foundation only recommends penis enhancement surgery for people with a rare condition called micropenis, where a penis is two or more standard deviations below the average size.

The American Urological Association states that there is not enough high quality evidence to support the safety or efficacy of penile augmentation surgery.

Potential risks of trying to increase penis size may include:

Genetics plays a substantial role in determining penis size. However, other factors, such as hormones, the environment, and nutrition, can affect penis size.

Other factors, including body type, physical fitness, and underlying medical conditions, may affect how the penis appears and a person’s perception. However, it is important to note that most people fall into the typical range of penis sizes.

A person can speak with a doctor if they have concerns about the size or appearance of their penis.