You've probably heard friends share stories about having sex with a guy who has a micropenis. Most likely, though, the man simply had a small penis, which is by no means the same thing.

Only a fraction of men have an actual micropenis. Yet if you find yourself with a micro guy (or are just plain curious), here are some things to know about the disorder—from why it happens to how its small size really affects sexual satisfaction.

What is a micropenis?

Micropenis is a real, diagnosable medical condition. It refers to a penis that is less than 2.5 standard deviations from what is normal for someone's age, "so it can vary a bit as you get older," observes Jamin Brahmbhatt, MD, urology and sexual health expert at Orlando Health. "Given this definition, anything less than around 3.65 inches when stretched or erect can be considered 'micropenis,'" he tells Health. In our size-obsessed world, having a micropenis can leave a guy feeling very self-conscious. And it can be a big surprise to his partner as well.

Typically, micropenis is diagnosed in newborn babies; it's not a condition that causes a normal-size member to suddenly shrink. "You cannot develop micropenis over time," says Dr. Brahmbhatt.

Micropenis is likely caused by a hormonal abnormality during fetal gestation, Arash Akhavein, MD, urologist at Comprehensive Urology in Los Angeles, tells Health. "The hormonal imbalance is thought to be low testosterone production at that stage, which normally should increase and cause the penis to become larger rapidly in a normal male fetus," explains Dr. Akhavein. “True micropenis is reported to be present in 1.5 in 10,000 born male children."

What size qualifies as micro?

When it comes to a baby’s penis, normal size is 2.5 centimeters (0.9 inches) in length. “Anything significantly smaller than that would be considered a micropenis,” Audrey Rhee, MD, urologist at the Cleveland Clinic, tells Health.

As for an adult member, the average length is 3.5 inches flaccid and 5.1 inches erect. As Dr. Brahmbhatt notes above, an erect micropenis clocks in at under 3.65 inches—slightly longer than the long edge of a credit card.

Psychologically, it can be tough

The psychological impact of having a micropenis is hard to underestimate. (Did you snicker when you read this article's headline? The name of the condition has the echo of a punch line.) "Any discussion of micropenis comes with social and cultural implications: What is it to be a man? How do men see themselves and how are they seen? By what standards are they judged?" Michael Reitano, MD, sexual health expert and physician-in-residence at the men's health service Roman, tells Health.

What a micropenis looks like, according to Reddit users

Reddit's "MicroPenis" community allows members to post dick picks and commentary. Anything having to do with small penises is fair game, and there are plenty of images involving rulers and common objects, like a soda can, a playing card, and a battery, for size.

It's clear, though, that some of the images do not meet the textbook definition of micropenis. Some are small, but not that small. Others are hidden within folds of fat. It's possible that some of these inconspicuous phalluses are examples of a condition known as "buried penis," not micropenis.

Treatment options for micropenis

"Sometimes you can give [an infant with a micropenis] a ton of testosterone in the first three months of life and get the penis to grow," says Dr. Rhee. Testosterone treatment can still be effective even after infancy so long as it's done prior to puberty.

Surgery, too, is an option. If a standard penile lengthening procedure isn't enough, a phalloplasty may be required, says Dr. Akhavein. "Phalloplasty uses tissues from other body sites (for example, the forearm muscle flaps) to create a new penis (and urethra) for the patient," he says.

What about sex with a micropenis?

Having a micropenis doesn't generally prevent men from getting erections, masturbating, having orgasms, or urinating, says Dr. Brahmbhatt. However, sometimes a micro guy will be unable to have penetrative sexual intercourse, points out Dr. Akhavein, which in turn may mean that assisted reproduction technology (such as IVF) is required to conceive a child.

"While micropenis can be a discomforting condition for some men, a fully satisfying sex life can be possible both for them and their partners," says Dr. Reitano, who adds that "from a functioning point of view, the size of a man’s penis is the least significant aspect of their sexual capacity to provide a partner the pleasure they desire."

Sex educator Kait Scalisi, MPH, recommends focusing on the sex acts that can be performed—not the ones that can't. "You can have a whole lot of fun and satisfaction from fingers, mouths, and toys," she tells Health. "Strap-ons and penis extenders augment your body. Vibrators stimulate the most sensitive part of the genitals, whether that's the clitoris, G-spot, prostate, or frenulum."

She suggests experimenting with positions. "Try variations of missionary where the receptive partner props their hips on a stack of pillows and then places their legs straight up to rest on the partner's chest and shoulders, while the penetrative partner kneels." Doggy style is another great option, she says, as larger penises can cause discomfort or pain. It's all about finding "creative solutions to enjoy each other's bodies," adds Scalisi.