Penis size varies amongst men, and in some cases, considerably. A study shows that neither race nor ethnicity has anything to do with penis size.
While many men may think they have above average size penises, most fall into the range experts consider normal size.
- Men who are dissatisfied with their penis size may look for ways to increase its size.
- As men age, their penises and testicles will experience some shrinkage.
- Many men report that their penis appears smaller when they gain weight.
Research on average penis size
Penis shrinkage is often caused by lifestyle or a treatable condition.
Research from BJU International finds average penis size falls within the following ranges:
- Average length of a flaccid penis: 9.16 centimeters (about 3.6 inches)
- Average length of a flaccid stretched penis: 13.24 cm (about 5.3 inches)
- Average length of an erect penis: 13.12 cm (about 5.2 inches)
- Average circumference of a flaccid penis: 9.31cm (about 3.7 inches)
- Average circumference of an erect penis: 11.66 cm (about 4.6 inches)
What are the causes of penis shrinkage?
Penis shrinkage is widespread as men age, but there are many other reasons why a penis may shrink:
As men age, fatty deposits build up in the arteries causing reduced blood flow to the penis. This results in the muscle cells in the erectile tubes inside the penis becoming weaker. The erectile tubes produce erections when they are engorged with blood, so less blood flow means smaller or fewer firm erections.
Another possible reason for penis shrinkage is a buildup of scar tissue caused by years of small injuries from sex and sports. This accumulation of scar tissue affects the spongy erectile tissues of the penis, causes penis shrinkage, and limits erection size.
The impact of weight gain, particularly around their stomachs, is a genuine concern for many men as they age.
Although a man's penis may appear smaller with weight gain, it has not shrunk. The reason it looks smaller is that the penis is attached to the abdominal wall, and when belly expands, it pulls the penis inward. If a man loses weight, his penis will regain its usual shape and size.
Research shows men who have had cancerous prostate gland removal surgery (radical prostatectomy) may experience some penis shrinkage. One report in the International Journal of Impotence Research found that 71 percent of men who underwent a radical prostatectomy experienced some penis shrinkage.
But researchers do not quite know why shrinkage occurs after a radical prostatectomy. Some researchers think it might be related to the urethral tube, which connects to the urinary bladder, shortening during the prostatectomy.
In Peyronie's disease, fibrous scar tissue develops inside the penis causing it to become curved during erection. Most of the time, a curved erection is not a reason for concern, but for some men, the bend might be significant or painful.
According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), Peyronie's affects up to 23 percent of men ages 40 to 70. It is possible that more men have this condition but have not reported it to their doctors due to embarrassment. While Peyronie's develops with age, it has been seen in men as young as 30, according to NIDDK.
Peyronie's can cause a reduction in length and circumference of a man's penis. Sometimes, Peyronie's goes away on its own; most of the time, however, it will either stay the same or get worse. Doctors will only consider treatment if the bend is painful or prevents sexual intercourse. Surgery can be done to remove scar tissue causing the shrinkage, bending, or pain.
Some medications can cause penis shrinkage. These medicines include Adderall, prescribed for attention deficit or hyperactivity, some antidepressants and antipsychotics, and some drugs prescribed to treat an enlarged prostate.
One 2012 study reported in the Journal of Sexual Medicine found that some of the male study subjects taking finasteride to treat enlarged prostate reported smaller penis size and reduced sensation.
One 2014 study reported in the journal Urology found that 41 percent of men taking dutasteride for the treatment of enlarged prostate experienced some form of sexual dysfunction.
Chemicals from cigarette smoking can injure the blood vessels in the penis, preventing the penis from filling with blood and stretching. Regardless of the stimuli and the effect on the brain, if the blood vessels are damaged, the penis will not achieve an erection.
A study carried out in 1998 by the Boston University of Medicine examined the erect penises of 200 men. According to one report, the results of the study found smokers had shorter erect penises compared to men who did not smoke. Researchers believe this is because smoking inhibits blood flow, preventing the penis from stretching, which might reduce penis length.
Smoking is also associated with erectile dysfunction (ED), this according to a 2017 study reported in the BJU International. ED affects a man's ability to maintain an erection, and smoking may prevent erections.
What are the treatment options?
Smoking may cause penis shrinkage due to chemicals affecting the blood vessels in the penis.
Most causes of penis shrinkage, such as smoking and weight gain, can be addressed by making lifestyle changes. If medications are causing the penis to shrink, an adjustment in medication can reverse the shrinkage.
For some men who experience penis shrinkage after prostate removal, the condition may improve on its own within a few months to a year. Penile rehabilitation (a form of physical therapy) after surgery can help men regain erectile function, and medications, such as Viagra and Cialis, can boost blood flow to the penis.
Treatment for Peyronie's disease focuses on removing scar tissue from inside the penis, either with medication, surgery, or ultrasound technology. Penis shrinkage is irreversible but repairing the curvature can help improve sexual function and reduce pain.
When to see a doctor
Most of the time, penis shrinkage is related to age, medication, or lifestyle habits, such as smoking or weight gain, and rarely requires treatment. Adopting more healthful lifestyle habits or changing medication can often reverse shrinkage and reduce other sexual problems.
Any man who is experiencing penis shrinkage, pain, or other sexual problems, or has concerns about cancer, should talk to their doctor. A doctor, or urologist, can answer questions, reassure male patients, and offer testing and treatment if necessary.