The Guide to The Penis

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Historically, there has been significant scientific debate over the importance of penis size. Yet no consensus has been reached. Many of our thoughts on penis size may or may not be grounded within reality. To better discern fact and fiction, we have researched the scientific literature.

By and large, the dominant belief of both male and female professionals (sex therapists, physicians, and psychologists) is that penis size is  biologically insignificant. Of greater social relevance, however, is the relationship between size and self-esteem. The goal of the Male Genitalia Kit is to help men feel better about themselves by exploring the wide variety of “normal” and then discussing the anatomy and physiology of the male genitalia. Use the button to your left to move forward to the Anatomy section. Penises come in all shapes, sizes, colors, and even textures. They have been the object of much scrutiny by science, the media, and artists, though the exact reason they take on such a symbolic and central role is unclear.

This site is divided into a number of sections. To get the most from this site, we recommend you begin with the Introduction section and continue down the list in order. You can move from section to section by clicking on the topics in the left frame.

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The male genitalia is composed both of the external genitalia (outside of the body) and the internal genitalia (within the body). The external genitalia consist of the penis, scrotum, and pubic hair. The internal genitalia, on the other hand, consist of a number of hidden glands and tubes that play a role in the production and delivery of sperm.


These include the epididymis (e), vas deferens (vas), and prostate gland (pr). Other internal structures seen in the drawing to the left are the pubic bone (PU), the urethra (u), and the testicle (T). For the sake of brevity, we will mostly focus on the external genitalia.

The most obvious aspect of the external male genitalia is the penis. The penis consists of a body (shaft) and glans (head). Under the skin (as shown in the picture of a dissected penis to the right) the body (B) or shaft of the penis contains three columns of tissue that can fill with blood to become an erection. The corpus cavernosum makes up the bulk of the penis tissue. At the underside of the penis is the corpus spongiosum (S) that also can fill with blood to form an erection. Running down the center of the corpus spongiosum is the urethra. The urethra is the tube which connects the bladder to the tip of the penis and is where both urine and semen exit. The penis is firmly attached to the pelvic bone by two strong bands of fibrous tissue, called the root. The root is not visible except when dissected. In this picture of a dissected penis (looking at the underside), the skin has been removed showing some of the underlying structures. The roots (R) join to become the body (B).

The tip, or head, of the penis is called the glans (G). It is one of the most sensitive areas on a man’s body due to the heavy concentration of nerve fibers. Unless circumcised, the glans is covered by a loose, hoodlike fold of skin called the foreskin (f) or prepuce. This foreskin can be pulled back exposing the glans. For those circumcised, the foreskin has been surgically removed just below the glans. There is often a wrinkle-like scar on the shaft at the site where the foreskin was removed.

Circumcision is a controversial procedure whereby the skin normally covering the head of the penis is removed. It is commonly done for religious or cultural reasons and a circumcised penis was believed to be medically superior in the past. Recent clinical studies have shown that although circumcised men do have a slightly lower rate of penile cancer and bladder infections when compared to uncircumcised men, the difference is insignificant. Today, most of the American medical community believes circumcision to be unnecessary at best, and cruel and disfiguring at worst.

f f f

A circumcised and uncircumcised penis. A cross-section through the shaft.

The vertical slit at the tip of the glans is the urethral meatus (m); it is the opening of the urethra (u). The urethra is a tube-like structure through which both urine and semen flow.


The base of the glans is a coned shape called the corona. Around the corona are numerous small sebaceous glands, which in latin are called glandula Tysonii odorifera. These glands secrete a whitish material which has a peculiar odor; this cheese-like substance is called smegma.

The scrotum is a loose, wrinkled pouch that has two compartments, each of which contains a testicle. The testicles are oval, rubbery structures that are about 4.5 cm long (range is usually 3.5 to 5.5 cm). The left testicle usually lies somewhat lower than the right. On the back side of each testicle is the softer, comma-shaped, epididymis (e); it feels somewhat like a bag of worms. Sperm leaving the testicle (where it is made), flows through the epididymis (e) into the vas deferens (vas), and joins the urethra (u) in the prostate (pr).


The first sign of puberty (usually around 9 1/2 to 13 1/2 years old) is an increase in the size of the testicles. Next, pubic hair appears and the penis begins to grow. The complete change form preadolescent to adult takes between 2 and 5 years. The entire process was studied by Dr. Tanner. His Sex Maturity Rating is used by the medical profession to determine what level of genital development has taken place.

Stage 1 is the preadolescent stage. There is no pubic hair (except for a fine peach fuzz similar to that on the belly and elsewhere) and the penis and testicles are in the same proportions as in childhood.

Stage 2
Stage 3
Stage 4
Stage 5

In Stage 2, there is sparse growth of long, slightly darkened, pubic hair at the base of the penis. The testicles begin to get larger, and the scrotum begins to get a reddened and altered texture. The penis may grow slightly or not at all.

In Stage 3, the pubic hair becomes darker, coarser, and curlier and begins to spread over the pubic bone (PU). The testicles continue to enlarge and the scrotum texture becomes more like that of an adult. The penis lengthens.

In Stage 4, the pubic hair grows to cover the base of the penis and begins to grown on the upper part of the scrotum. The hair gets darker, coarser, and curlier. The scrotal skin gets darker as the testicles continues to grow. The penis continues to grow longer, and gets wider. The glans, or head, of the penis becomes much more prominent.

In Stage 5, the pubic hair has spread to the inside of the thighs. The scrotum, testicles, and penis grow to their final adult size and shape.


To gain an erection, blood vessels at the entrance of the penis open up and allow blood to flow in. The blood (warm and therefore red, in the heat-sensitive photo) then enters the sponge-like tissue of the corpus cavernosum and corpus spongiosum. As the blood fills into the penis, an erection forms. Erections are brought about through the parasympathetic nervous system when the penis and other erogenous zones are stimulated. In addition, certain sights, sounds, smells, thoughts and dreams (either day-dreams or night-time dreams) can trigger the blood vessels to open and an erection to form. From early childhood onwards, erections occur during sleep. This phenomenon, called nocturnal penile tumescence, occurs during REM sleep (Rapid Eye Movement) and usually occurs for about 100 minutes a night. Having an erection upon wakening in the morning is an example of this phenomenon.

With continuing stimulation, an orgasm can occur. The orgasmic expulsion of semen from the penis (ejaculation) is a reflex and not physiologically dissimilar to a “doctor checks your knee” type of reflex. While an erection can be interrupted at any moment by will (or from fear), the ejaculation reflex, once started it cannot be stopped. Once triggered, the reflex begins with the movement of sperm from the epididymis (e) (where sperm is stored after being made in the testicle) to the vas deferens (vas). The sperm moves into the prostate (pr), and mixes with secretions from the prostate and seminal vesicles and is then expelled through the urethra. In healthy adults, about 3 cc of semen (containing 300 million sperm) are released with each ejaculation.


Correctly Measuring Your Erection

Erections come in all shapes and sizes, and can even vary from one measurement to the next. Correct evaluation of the data requires measuring yourself in the manner in which the study participants measured their penis size. To correctly measure your erection length and circumference, you will need the following:

1. Ruler and 6 inches of string.

2. Pencil and the calculation sheet.

3. Once you have these items, continue on by clicking here.



Erections come in many shapes and sizes as seen in the photos on this page (which is longer than most). Data on erect penis size obtained by measurements from 4,982 people is arranged in the following table and graphs. Click on the table and graphs listed below to see erection data displayed. All data are from reputable scientific journals (listed in the references section).

A few important notes before comparing yourself: First, the data upon which these graphs is based on is derived from Caucasian and African Americans. People of Asian and other ethnicities were not included in the data and for these demographics this information may not be as applicable. We are currently working on data for non-Caucasion/non-African-American individuals.

Second, keep in mind that erection size will differ depending on the level of arousal, time of day, room temperature, and recency of sexual activity. (The studies from which these data were obtained did not standardize these variables.) In addition, the presence of foreskin technically increases the final length by a small amount (about an eighth of an inch). Penis curvature also will play a role in  measurement. Most of these minor variations, unless otherwise noted, are not accounted for in data.

g g g g g
Graph your length compared to nearly 5000 men by using this pull-down menu:

For additional analysis of this data, click on the following:

1. Table of Average Erection Length Based on Age

2. Pie Chart Graph of Erection Sizes

3. Graph of Erection Circumference compared to others

4.’s user survey results



1. Women prefer men to have a big penis.
False2. A “normal” erect penis should point straight.
False3. A big penis when flaccid (unerect), will be a big penis when erect.
False4. Tall (or big) men have bigger penises than short (or small) men.

5. African Americans, as a group, have bigger penises than Caucasians.
Score =
View the answers


There are many different types of diseases that can affect the genitals. They are classified by whether they are acquired (after birth) or congenital (born with the disease). The acquired diseases can be further classified by whether they are associated with problems with inflammation (infection), cancer, blood flow, or some combination of problems leading to dysfunction.

Perhaps the most common disease affecting men is sexual dysfunction. This is the failure to achieve adequate erection, ejaculation, or both. Men with sexual dysfunction may complain of loss of sexual desire (libido), difficulty or inability to initiate or maintain an erection (impotence), failure of ejaculation, premature ejaculation, or an inability to achieve an orgasm.


Other than sexual dysfunction, some of the most common acquired diseases are infections caught from a partner during sexual contact. Diseases such as chlamydia, herpes, genital warts, and HIV/AIDS are just some of the more common sexually transmitted diseases. (The photo shows the milky penile discharge of man with gonorrhea.) A detailed look at the major sexually transmitted diseases is beyond the scope of this guide, but is currently available in our Sexually Transmitted Disease (STD) Online Guide. The guide shows photographs and gives detailed information on detecting, curing, and preventing common sexually transmitted diseases. With the exception of sexual abstinence, the regular and correct use of condoms is the best way to avoid the sexually transmitted diseases.


A non-sexually transmitted disease causing inflammation and rarely sterility is mumps. Though the mumps virus commonly causes only swelling of the salivary gland (parotitis), about 10% of men will get swelling of the testicle (mumps orchitis). Luckily, one of the childhood vaccinations protects us from mumps (the MMR immunization, or Measles, Mumps, and Rubella).


Skin abnormalities also affect the genitalia. Eczema and psoriasis can cause redness, scaling, and itchiness. Fungal infections, like jock-itch (tinea cruris) also affect the skin of the scrotum as pictured here. Treatment of this rash is with an antifungal medication. Other fungal infections, like candida balantitis is also treated with medication.

Peyronie’s disease is the formation of scar-like tissue on the penis. This can lead to abnormal curvature and painful erections. Peyronie’s disease is usually felt as a fibrous plaque on the underside of the penis. Surgical treatment by a urologist is often required in advanced cases.


The abnormal growth of cells (cancer) can afflict essentially any part of the male anatomy. Testicular cancer generally affects young to middle-aged adults and is the leading cause of death from solid cancers in men between the ages of 15 and 32. There are many different types of testicular cancer depending on which type of cell begins to grow abnormally. (The photo is of a patient with lymphoma that has spread to the testicle.) Testicular cancers have a good cure rate when caught early, so discovering the tumor is important. A testicular self-exam done monthly by all men aged 15 and older can detect these usually symptomless tumors. Click here to learn how to do a testicular self-examination.

Cancer of the penis accounts for roughly 1% of all male cancer. Such cancers are usually slow growing but can spread to surrounding lymph nodes and tissues, thereby making a cure more difficult. The photo shows a man with a cancer that has eaten away a significant amount of the tip of his penis. Obviously, any new or non-healing growth on the penis (or elsewhere), should be shown to your doctor. Check out our Skin Cancer Guide for more information and photographs.


Prostate cancer is the second most common cause of male cancer deaths (after lung cancer), and is most often found in men older than 50. The cancer seldom produces symptoms until it spreads, so prostate screening (rectal exam and possibly a blood test) is important for early diagnosis and treatment.

Congenital problems with the male genitalia are caused during fetal development. The most common abnormality is failure of the urethral tube to form correctly resulting in an additional hole in the penis. This additional hole is usually located on the underside (hypospadias – pictured) or top side (epispadias) of the penis and is usually not a significant problem. The result of having a hypospadias or epispadias is that urine and semen exit the penis from more than one site. Another fairly common abnormality is a phimosis. This is defined as an abnormally small opening of the foreskin. It can be congenital or acquired (from infection). Having a phimosis is a problem because it can lead to further infection and even some types of cancer due to the chronic accumulation of secretions and other debris under the foreskin (smegma). A surgical incision or circumcision is the treatment of choice for phimosis. Congenital anomalies of the testicle also occur occasionally. An undescended testicle (cryptorchidism) is the most common birth defect affecting up to 0.8% of newborn males (1 out of every 125) . If the testicle has not descended into the scrotum by 1 year of age, it needs to be surgically lowered (or removed), as a large number of undescended testicles will become cancerous.


Impotence is the failure to achieve erection and/or ejaculation. Men with sexual/erectile dysfunction may complain of one or more of the following: loss of sexual drive (libido), inability to initiate or maintain an erection, ejaculatory failure, premature ejaculation, or inability to achieve orgasm. Transient periods of sexual problems and impotence are not considered erectile dysfunction and probably occur in half of all adult males at some point in their life. It is estimated that nearly 30 million American men suffer from true erectile dysfunction. This means that one out of every ten men have some difficulty achieving and/or maintaining an erection on a regular basisThere are many causes of erectile dysfunction (ED). It is estimated that 60% of ED is due to psychological issues such as self-esteem problems,  sexual anxiety/performance anxiety, or problems with interpersonal relationships (feelings of guilt, fear, or prior traumatic experiences). Medical (organic) illnesses make up the other causes of ED (e.g., high blood pressure, heart disease, diabetes, hormonal problems, spinal cord/brain injury, depression, etc). A combination of both psychological and organic problems is quite common and is believed to be the case in a majority of patients. Many medications used to treat other illness, including the medical problems listed above, can themselves cause ED! Click here for a list of common drugs and medications that can cause sexual and erectile dysfunction. There are a many of treatment options for erectile dysfunction. These include counseling and sex therapy, medications (e.g., Viagra), and medical (and non-medical) devices and apparati.


Premature ejaculation is defined as consistently ejaculating before you want to. Unfortunately, societal emphasis on ejaculation as the goal of intercourse exacerbates the “performance anxiety“ that often causes premature ejaculation in the first place. Men may try a number of strategies to delay ejaculation such as thinking of baseball scores or doing multiplication tables. Some of these techniques can cause men to be emotionally detached during intercourse. Some techniques that are less distancing include:

Take a more global, less penis-centric approach to pleasure. Try the “squeeze technique.” Simply squeeze the head of the penis by hand as ejaculation approaches, wait until the response passes, and then continue. Use an extra strong (and thereby less thin, and sensitive) condom. Increase the frequency of ejaculations. Talk to a therapist. Consider medications.

A common side effect of one class of antidepressants is “sexual dysfunction.” These Selective Serotonin Reuptake Inhibitors (SSRI) medications such as Prozac, Zoloft, Paxil, Celexa, and others, actually can inhibit the ability to ejaculate. Because of this, they have been used by some clinicians in the treatment of premature ejaculation. Your doctor or therapist can give you more information on this treatment.

For more detailed information on this issue, check out the following books:

How to Overcome Premature Ejaculation (by Helen Singer Kaplan)

Impotence Assist: The Causes, Treatments, and Prevention of Weak Erections (Impotence) and Premature Ejaculation (by Dr N Beck)

Additional excellent books on this and other topics can be found in the Resources section.


Men aged 15 and older should regularly examine their scrotum looking for any abnormalities or changes. (The man on the right has a testicular lymphoma – usually lumps and bumps are much smaller and not as “angry-looking.”) A monthly self-exam is important, as is an annual doctor’s exam. Since most testicular cancers have no symptoms, the only way to diagnose it early is to be on the lookout.

To correctly examine yourself, follow these instructions:

1. Check yourself right after a hot shower. The scrotal skin should be relaxed and soft.

2. Become familiar with the normal size, shape and weight of your testicles. It is common for one testicle (usually the left) to be larger and hang lower than the other.

3. Using both hands, gently roll each testicle between your fingers.

4. Identify the epididymis, a rope-like structure (like a bag of worms) on the top and back side of each testicle. This structure is not an abnormal lump.

5. Always be on the lookout for a tiny lump under the skin, in the front or along the sides of either testicle. A lump may remind you of a kernel of uncooked rice or a small hard pea.

Other things to be on the lookout for are:

  1. one testicle may swell, or feel abnormally heavy
  2. your breast may enlarge and feel tender
  3. a sore may develop which does not heal
  4. a small painless lump may develop on a testicle

Always report any swellings, lumps, abnormalities, or concerns to your doctor immediately. Keep in mind that most of the lumps and bumps you discover will not end up being cancerous, and even if they are, most are completely curable and will not significantly effect sexual activity or the ability to have a child.


As far back as 1350 BC, there are records of Egyptian men wearing sheaths as decorative covers for their penises. In the eighteenth century, condom use became popular for protection against infections and unwanted pregnancies. The condom is usually made of latex rubber (another name for it is “a rubber”) and is meant to fit an erect penis. Many condoms come lubricated and/or premedicated with spermicide (a chemical that kills sperm cells on contact). Other condoms made of lamb intestines are more expensive and may not protect as well against sexually transmitted diseases. Condoms are designed to keep semen from getting into the woman’s vagina. To maximize the protective benefits of condoms, they must be used correctly.

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Condoms usually come rolled up in a package. It will unroll to about 7 1/2 inches, though one should not unroll it until putting it on the erection. A 1 3/8 inch ring is found on the open end to help prevent the condom from slipping off during use. The closed end often has a nipple reservoir that catches semen and helps prevent the condom from breaking. A high-quality latex condom has a failure rate of 1% – 2%, meaning that one can expect their condom to break, burst, contain a minute hole, or slip off, once or twice every 100 times of use. Because of this, only abstinence is completely effective at preventing STDs.

To use a condom correctly, pinch the end (the nipple) to get the air out prior to placing it on the head of the penis. This pinched-off space will be where the ejaculate collects and minimizes the risk of bursting the condom. Roll the condom down the shaft of the erection, covering as much skin as possible (many STDs can spread from skin to skin contact even if there are no open sores or rashes present). The condom must be unrolled onto the erection before any intercourse occurs as it is common to leak a small amount of semen from the stimulated penis prior to ejaculation. If you are not using a lubricated condom, you should put K-Y Jelly or a spermicide onto the condom once it has been placed on the erection to lubricate and hence minimize the risk of tearing the condom during sexual relations. NEVER use Vaseline (petroleum jelly) on the condom as it can dissolve the latex. When withdrawing the condom-covered penis from the vagina or mouth, be sure to hold the rim to prevent it from slipping off and spilling sperm onto mucous membranes. In case of an accidental spill around or in the vagina, insert spermicide cream, jelly, or foam gently in and around the vagina. Do not douche.

Condoms can be bought at any drugstore, and usually come packaged in sets of 3 to 12. To order condoms-by-mail, discretely and inexpensively, check out our hardcopy male genitalia kit, or click on the condom picture.


This online kit has discussed the male genitalia from anatomy to function to disease. It has also enabled you to measure and compare your erection to the population. The knowledge of how you measure up may be pleasing or distressful to you. We at understand the instinct of many men to compare themselves to others, yet scientific literature reports that penis size is both unpredictable and unimportant. By medical standards, any erect penis two inches or longer is considered normal and adequate for reproductive purposes. In the scope of our lives and relationships, penis size means very little. We hope that this kit has allowed you to recognize that your erection is most likely within average limits, and normal.

For those of you who remain deeply unhappy with your penis, there are a few techniques to change your size or shape. The least expensive and easiest technique is too lose extra body weight. Most overweight men store fat in their lower abdomen just above where the penis is attached. This fat literally hides a portion of the penis making the overall length look smaller. It has been shown that an overweight man losing 35 pounds, will gain an extra inch of penis length! Other techniques can be used to increase the power of an erection. Products such as suction devices are discussed in the section on sexual dysfunction. Penile Augmentation Surgery (PAS) is another, much more drastic, technique for increasing or changing ones penis size.
For more detailed information on this and other topics, there are a number of excellent books that you can get delivered and be reading in the privacy of your own home within a day or two. Click on the title below to get them right now through (at a significant discount).
1. The Penis Handbook: An Owner’s Manual (by Margaret Gore)
2. The New Male Sexuality (by Bernie Zilbergeld, Ph.D.)
3. Illustrated Manual of Sex Therapy (by Helen Singer Kaplan, David Passalacqua (Illustrator))
4. Impotence Assist: The Causes, Treatments, and Prevention of Weak Erections (Impotence) and Premature Ejaculation (by Dr N Beck)
5. Facts and Phalluses: A Collection of Bizarre and Intriguing Truths, Legends, and Measurements (by Alexandra Parsons)
6. Penis Enlargement Facts and Fallacies: All Men Are Not Created Equal (by Gary Griffin)

One of the best resources for information is your own doctor. He or she can give you valuable input on your genitalia and whether there really is something wrong. To get the doctor’s input, however, you need to ask. Most doctors are perfectly comfortable discussing this topic, but won’t initiate such a talk.

If all else fails, pick up the Yellow Pages and look for a urologist (under “Physicians”). These doctors specialize in the genito-urinary tract (sex organs and urine system). Many urologists either subspecialize in sexual difficulties, or can refer you to a colleague who does. Some options include suction appliances, hormonal and medicine therapy, surgery, and prosthetics. But be careful, if you call an unscrupulous doctor, they may want to treat you whether or not it is needed.

We hope you will have a fun and responsible time with your genitalia.

Other references used in the production of this guide.

Baker RR and Bellis MA: Human Sperm Competition, London, 1995, Chapman & Hall

Fisher WA, Branscombe NR, and Lemery CR: The Bigger the Better? Arousal and Attributional Responses to Erotic Stimuli that Depict Different Size Penises, Journal of Sex Research; 1983: 19 (4), 377-396

Gebhard PH and Johnson AB: The Kinsey Data: Marginal Tabulations of the 1938-1963 Interviews Conducted by the Institute for Sex Research, Philadelphia, 1979, W. B. Saunders

Jamison PL and Gebhard PH: Penis Size Increase Between Flaccid and Erect States: An analysis of the Kinsey Data, Journal of Sex Research, 1988: 24, 177-183

Metz ME, Seifert, Jr. MH: Men’s Expectations of Physicians in Sexual Health Concern, Journal of Sex & Marital Therapy 1990: 16, 79-88

Masters WH and Johnson VE: Human Sexual Response, London, J & A Churchill, 1966

Rosen RC and Keefe FJ: Measurement of Human Penile Tumescence, Psychophysiology, 1978: 15, 366-376

Siminoski K and Bain J: The Relationship Among Height, Penile Length, and Foot Size, Annals of Sex Research, 1993: 6 (3), 231-235

Schonfeld WA and Beebe GW: Normal Growth and Variation in the Male Genitalia from Birth to Maturity, Journal of Urology, 1942: 48, 759-777


The following drugs and medications have, in some instances, been shown to cause erectile or sexual dysfunction in some patients. Many other medications that are not listed may also cause erectile dysfunction. If you are taking one or more of these drugs, and you believe it is causing erectile or sexual dysfunction, do not stop taking it until you have discussed it with your doctor. Stopping some of these medicines “cold-turkey” can actually lead to high blood pressure, stroke, or other serious problems!

  • alcohol
  • anti-androgens (ketoconazole, spironolactone)
  • antiarrythmics (digoxin)
  • antidepressants (e.g., prozac, zoloft, paxil, mao-inhibitors, elavil, nortriptyline)
  • antihypertensives (beta-blockers like atenolol, inderal, metoprolol, propranolol, lopressor; diuretics like hydrochlorthiazide (HCTZ), maxide, calcium channel blockers (cardizem, verapamil, norvasc), ace inhibitors (vasotec, lisinopril), and others like clonidine, methyldopa)
  • barbituates & narcotics (e.g, codeine, heroin, methadone, morphine, percocet)
  • benzodiazepines (e.g., ativan, librium, serax, tranxene, valium, xanax)
  • cocaine
  • H2-blockers (cimetidine)
  • marijuana


  • Print this page and use it to record your measurements.
  • Once you have printed this sheet, return to the Measure My Penis page.

Record Your Erection Length

A. Enter your measurements in the spaces provided below. For more accurate results, an average of three measurements will be used. 1. Erect penis length, 1st measurement: ___________inches 2. Erect penis length, 2nd measurement: ___________inches 3. Erect penis length, 3rd measurement: ___________inches

B. Calculate the average. 4. Add the three values together: ___________ 5. Divide this number by three:___________ 6. AVERAGE penis length: ___________inches Record Your Erection Circumference (girth)

C. Enter your measurements in the spaces provided below. For more accurate results, an average of three measurements will be used. 7. Erect penis circumference, 1st measurement: ___________inches 8. Erect penis circumference, 2nd measurement: ___________inches 9. Erect penis circumference, 3rd measurement: ___________inches

D. Calculate the average. 10. Add the three values together: ___________ 11. Divide this number by three.

E. AVERAGE penis circumference: ___________inches


As with anything you put near your genitals, be careful to avoid injury.


Penis length is defined as the linear distance along the dorsal side of the erect penis extending from the mons veneris to the tip of the glans. In non-medical terms, the penis length is measured in a straight line on the top side of the erect penis, from the skin of your belly to the tip of your penis. Penis circumference is defined as the linear distance around the widest, thickest, part of the erect penis (see below). 1. Stimulate yourself into the erectile state. 2. Place your ruler on the skin of your bellyand at the base of your erect penis. While you should not push in against the skin, some of the studies used in this guide allowed the measurer to push in to the bone beneath the skin (pubic bone). 3. Press the ruler against your penis and read the nearest quarter-inch measurement at the tip of your penis. (In the example shown, the measurement would be 4 and 3/4 (4.75) inches.) 4. Record this number in the space provided on the calculation sheet or on your paper. 5. Repeat this measurement two more times, preferably with different erections and preferably on different days as penis size will differ depending on the level of arousal, time of day, room temperature, and recency of sexual activity. (The studies from which these data were obtained did not standardize these variables.) PENIS CIRCUMFERENCE Penis length is not the only factor in determining penis size. The width, girth, or fatness, of a penis is also an important aspect when making comparisons. Most people have a penis that is either longer and thinner, or shorter and fatter. To compare how the girth of your penis compares to the population, use the instructions below to determine your penile circumference (distance around the widest part of your penis). 1. Stimulate yourself into the erectile state. 2. Place the fabric ruler or string end at the widest part of your penis and wrap it carefully around one time. Mark the spot where the string first touches itself. 3. If using string, take the marked string and lay it against the ruler. Read to the nearest quarter-inch measurement. 4. Record this number in the space provided on the calculation sheet or on your paper 5. Repeat this measurement two more times, preferably with different erections and preferably on different days as penis size will differ depending on the level of arousal, time of day, room temperature, and recency of sexual activity. (The studies from which these data were obtained did not standardize these variables.)


Another way to determine how your penis compares to the entire male population is to use a pie-chart. To determine your “slice of the pie”, find your erect penis length on the pie-chart. The size of your pie-chart slice represents what segment of the population has the same erection size as you. The remainder that is found counter-clockwise to your slice to the 12 o’clock position represents the portion of the population that has a shorter penis. The portion of pie found clockwise to your slice has a longer penis. For example, if your erection is 6 1/4 (e.g., 6.25 inches), then 9.8% of the population also has a 6.25 inch erection. Looking counterclockwise, 48.8% of the population has an erection that is less than 6.25 inches (e.g., 24.4 + 5.3 + 8.1 + 3.4 + 7.6 = 48.8). Looking clockwise, 41.2% of the population has an erection that is longer than 6.25 inches (e.g., 15.6 + 6.0 + 10.0 + 9.6 = 41.2).


Graph III. Erection Circumference Compared to Percentage of Population

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Or, to plot your measurement on this curve, use the pull-down menu:



Facts & Fiction Answers

1. Women prefer men to have a big penis. False

A 1983 study (Fisher et al.) asked 154 woman undergraduate students to read a number of erotic passages which differed only in the size of the male penis in the story. The women were then asked a standard set of questions to determine their level of arousal. The study found that, in general, penis size was an unimportant factor in the level of arousal of these women. A survey of women by the Diagram Group in 1981 showed that when asked to what part of a man’s body do woman pay most attention, 39% said the buttocks. Only 2% of women indicated an interest in the penis. Other studies (e.g., Masters and Johnson, Hite, Wolfe) have shown that penis size has very little to do with either a woman’s stimulation during intercourse, or the probability that she will reach an orgasm. In summary, the literature reports that the vast majority of women don’t care if a man has a small, medium, or large penis.(the latter half is more important than the former)

2. Normal erect penises should point straight. False

Tabulation and analysis of the Kinsey Data (Gebhard, et al.) showed that approximately 50% of penises do indeed point straight. The remaining 50% pointed in a variety of directions. They found that 30% pointed straight up, 10% pointed to the left, 6% pointed down, 3% pointed to the right, and the other 1% pointed in some combination of these directions (i.e., up and left). (This data did not adequately describe curved penises, namely those that start out pointing straight then curve off in another direction.) 3. A big penis when unerect, will be a big penis when erect. False A 1988 study (Jamison et al.) looked at the change in size when going from an unerect (flaccid) state to an erect state. The study compared two groups of men, those with smaller flaccid penises and those with bigger flaccid penises. Although they found relatively large variations in flaccid penis size between men when  erect, the differences disappeared. In other words, smaller flaccid penises grow significantly more than larger flaccid penises such that when erect both penis groups are essentially the same size. A Masters and Johnson study (1966) also described this phenomenon. Put another way, the volume (length X circumference) of everybody’s penis is similar; longer penises are thinner, shorter penises are fatter. 4. Tall men have bigger penises than short men. False A 1993 study (Siminoski et al.) analyzed the relationship between penis size, body size, and foot size, based on the folklore that tall, big-footed men had big penises. 63 virile men (aged 27-71 years) were measured. The study found that although tall height and large shoe-size were weakly correlated to larger penises, differences were minimal and statistically insignificant. 5. African Americans have bigger penises than Caucasians. True As a group, African Americans do have slightly longer and thicker penis than their Caucasian counterparts. This is shown on these graphs.


Bar Graph: Black v White Penis Size at Various Lengths & Circumferences



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