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What You Should Know About Penis Size


Men obsess over penis size. We won’t try to change that. So here are some facts, based on the best scientific research we could find.

Average Penis Size

The average penis size is smaller1 than most men think.

Flaccid Length3.619.16
Flaccid Girth3.669.31
Erect Length5.1613.12
Erect Girth4.5911.66

Penis length was measured on the top of the penis, from the public bone to the tip of the penis. Any fat covering the pubic bone was compressed before measurement, and any additional length provided by foreskin was not counted. 

Penis girth (circumference) was measured around the midpoint of the shaft.

Flaccid size varies more than erect size; as the saying goes, some men are “showers” and some men are “growers.”

There are many websites that claim penis size varies by race or nationality, or that it is tied to physical traits like the length of the nose or size of the foot. These claims are based on “junk research,” and the data from large-scale scientific studies does not support them.

What is Normal?

An erect penis length of approximately 4″ to 6″ is considered normal.

There are a small number of men who suffer from a condition called micropenis, in which the penis does not develop normally, usually due to a hormonal imbalance during the mother’s pregnancy. A micropenis is less than 3.2″ (8.1 cm) when erect. This condition affects less than 0.6% of all men.

It’s also possible for a normal penis to shrink. Medical conditions that prevent proper blood flow to the penis can cause tissues to contract, resulting in smaller length and girth. This is particularly common in men following prostate removal surgery.

Whatever your penis size, you can have a satisfying sex life. (See our article “A Great Sex Life with Erectile Dysfunction“)

Can You Increase Penis Size?

There are many claims made for treatments to increase penis size, but with few exceptions, there is no clinical evidence to support these claims. Here’s a run-down:

Penis Extenders and Traction Devices

A normal penis can also by enlarged using a traction device. These devices are attached to the penis and actually stretch it. This results in microscopic tears in the tissue of the penis, which the body “heals” by growing new tissue.

However, the devices must be worn for long periods of time – typically two 2-hour sessions each day, for 6 months. A six-month trial showed an average increase of approximately half an inch (1.2 cm)2. Another study showed a slightly larger increase (.66 inches, or 1.7 cm)3. A 2011 study found that wearings a traction device 4-9 hours per day for three months could increase penis size by up to an inch4.

The RestoreX®, a penile traction therapy device developed in cooperation with the Mayo Clinic, has shown significant improvements when used for just two 30-minute periods per day, over three months.

Note that these are very small studies, and further research is needed.

Herbal Remedies

Many herbal products claim to increase penis size. Without exception, these claims are unsupported.

Furthermore, there are significant risks associated with using herbal supplements. (See our article, “Herbal Remedies for ED.”)

Penis Pumps

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Clinical studies show that Vacuum Erection Devices (aka Penis Pumps) do not significantly increase penis size5 6.

They can, however, restore length after shrinkage caused by blood flow problems7. In order to accomplish this, the pump must be used regularly – ideally, two 15-20 minute sessions each day.

Platelet-Rich Plasma (PRP) Injection Therapy

PRP injection therapy involves drawing the patient’s blood, concentrating the platelets, and then re-injecting it into the penis. There are claims that PRP injections can increase penis size by stimulating tissue growth. There is no clinical evidence to support these claims.


Jelqing is a massage technique that forces blood into the penis and stretches it.

There is no evidence that this increased penis size. This is not surprising, considering the amount of time required for penis extenders to show results.

If not done properly, jelqing can result in bruising or even permanent damage to the penis. Some doctors report patients with Peyronie’s disease – scarring and deformity of the penis – as a result of jelqing.

Weight Loss

Although losing weight won’t increase the size of your penis, getting rid of fat – particularly belly fat – can make the penis appear bigger.


Trimming or shaving your public hair can make your penis appear bigger, and also make oral sex more pleasant for your partner.

Does Penis Size Matter?

Maybe, but not much.

A recent study allowed women to choose their “ideal” size from among a range of plastic cylinders. On average, they chose a penis that was 6.3 inches long, and 5 inches in circumference7 . This is slightly larger than the average size of actual penises, but well within the normal range.

The selection was made by visually inspecting and handling the fake penises. The women were not given the chance to “try out” the penises, which might have changed their preferences.

Various informal surveys and studies indicate that most women prefer greater girth rather than greater length.

The average vagina is 4.25″ to 4.75″ inches deep when aroused, and most of the nerve endings are in the outer third. Having an extra-long penis probably doesn’t contribute much to the woman’s pleasure, and can actually be painful.

The bottom line is that, the “average” penis and the “average” vagina are a pretty good fit! Rather than obsessing over length, men would be better off learning how to improve the quality of their sexual relationships.


  1. Veale, David; Miles, Sarah; Bramley, Sally; Muir, Gordon; Hodsoll, John. “Am I normal? A systematic review and construction of nomograms for flaccid and erect penis length and circumference in up to 15,521 men.” Sexual Medicine. Dec 8, 2014. <>
  2. Nowroozi, M R; Amini, E; Ayati, M; Jamshidian, H; Radkhah, K; Amini, S. “Applying extender devices in patients with penile dysmorphophobia: assessment of tolerability, efficacy, and impact on erectile function.” Journal of Sexual Medicine. May 2015. 12(5):1242-7.
  3. Gontero, P; Di Marco, M; Giubilei, G; Bartoletti, R; Pappagallo, G; Tizzani, A; Mondaini, N. “A pilot phase-II prospective study to test the ‘efficacy’ and tolerability of a penile-extender device in the treatment of ‘short penis’.” BJU International. Mar 2009. 103(6):793-7. <>
  4. Nikoobakht, Mohammadreza; Shahnazari, Alireza; Rezaeidanesh, Maedeh; Mehrsai, Abdolrasoul; Pourmand, Gholamreza. “Effect of penile-extender device in increasing penile size in men with shortened penis: preliminary results.” Journal of Sexual Medicine. Nov 2011;8(11):3188-92.
  5. Aghamir, M K; Hosseini, R; Alizadeh, F. “A vacuum device for penile elongation: fact or fiction?” BJU International. Apr 2006; 97(4):777-8.
  6. Spitz, Aaron. The Penis Book. Rondale Wellness. 2018. Pp 53-43.
  7. Prause, Nicole; Park, Jaymie; Leung, Shannon; Miller, Geoffrey. “Women’s Preferences for Penis Size: A New Research Method Using Selection among 3D Models.” Plos One. 2 Sep 2015.

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