Women who've had one night stands, casual sex, and relationship sex can all admit they've at some point had unrealistic expectations when it comes to penis size. Although it's unclear whether beer goggles or porn actors — or both? — are to blame, women across the world are in disagreement about how big or small a man’s penis actually is. In an international survey, researchers found both men and women greatly overestimate the average length of men's penises.

Previous studies have found the length of the average erect penis is a little more than 5 inches long and 1.5 inches in diameter. Specifically, a 2013 study published in the Journal of Sexual Medicine found the average American man’s penis is 5.6 inches long when erect and 4.8 inches in circumference. Only 15 percent of penises are over 7 inches, and only 3 percent are over 8 inches.

Penis Size Passers by look at various sets of condoms displayed during an anti-AIDS campaign in Seoul, South Korea on Nov. 30, 2004. Wang Jun-Young/AFP/Getty Images

To put things in perspective, British online medical website Dr. Ed, asked more than 2,100 women and men, between the ages of 18 and 75, to guess the length of the average erect penis and tell it what an ideal penis is, length-wise. Nearly half the respondents were from the United States and the rest lived in nine different European countries, including Britain and the Netherlands. Sexual identity and the ethnicity of the respondents were not taken into account.

Unsurprisingly, men and women from across the world, have a skewed perception of erect penis size. Female participants guessed that the average was 5.4 inches, while the men estimated an average of 5.6 inches. Penis estimation also varied by country. In Poland, people believed the average penis size was 6.2 inches long while Brits said it was 4.9 inches. Even in the U.S. estimations were scattered, with Maine respondents giving the largest estimattion at 6.5 inches; West Virginians gave the smallest estimations even though they were closer to reality, at 5 inches.

Among all the 10 countries surveyed, people thought the "ideal" penis was longer than the perceived average penis. The U.S. had the largest gap between the perceived average penis and the ideal penis, with a difference of 1.1 inches. In comparison, those in the Netherlands were most satisfied, believing the ideal penis was 0.4 inches larger than the perceived average penis.

Overall, it seems like there is no universal average penis size or ideal penis. Instead, there are plenty of unrealistic expectations about male genitalia, like size. This is why many men are obsessed with size, and particularly the length, of their penises, seeking penis enlargement surgery.

To enlarge the penis, surgeons cut the suspensory ligament, which connects the penis to the pubic bone and supports it when erect, to release tension so more of the shaft becomes outwardly visible. However, to prevent the ligament from reattaching, the patient will most likely need to attach weights or stretching devices to their penis daily for approximately six months. To widen the penis, surgeons use an implanted allograft — tissues harvested from cadavers — to stuff the penis, according to Dr. Mark P. Solomon, a plastic surgeon in Philadelphia.

A 2014 study found Germany has the highest number of penis enlargement operations in the world. Out of an estimated 15,414 enlargements worldwide, 2,786 operations took place in Germany, or eight out of every 100,000 male adults. This accounts for 18 percent of all male enhancement surgeries in the world. Venezuela was runner-up, with four out of every 100,000 adults undergoing the nip-tuck procedure.

Whether penis size really matters actually depends on who you ask. A number of things influence how the penis appears, including a man's body size and shape, penis girth, and whether or not he manscapes. While most men who think their penis is too small may consider one penis enlargement, chances are they actually have a normal-sized penis. This means we need to have more realistic expectations when it comes to the human body.