Average penis size: what the studies show

Most men think the average penis size is bigger than it is. A 2021 review by King, of the psychology department at Clemson University in the US, says most men believe the average erect penis is longer than 6 inches, partly because often-cited studies relied on men's own measurements. Those studies averaged about 6.2 inches for heterosexual men and suffered from volunteer bias and social desirability bias.

The figures on this page come from studies where a health professional or researcher did the measuring.

What is the average penis size?

A 2015 review of men measured by health professionals puts the average male penis at 13.12 cm (about 5.2 inches) long when erect and 11.66 cm (4.6 inches) around. Soft, the average length was 9.16 cm (3.6 inches). Two later reviews of measured men came to similar figures.

The 2015 review was led by Veale and colleagues at the Institute of Psychiatry, Psychology and Neuroscience in London. It pooled studies in which a health professional measured each man with a standard procedure, with at least 50 men in each sample, and built charts of normal size from up to 15,521 men.

Average penis length and girth: the measured averages

	Average.	In inches.	Men measured.
Soft (flaccid) length	9.16 cm	3.6	10,704
Soft length, stretched	13.24 cm	5.2	14,160
Erect length	13.12 cm	5.2	692
Soft girth (circumference)	9.31 cm	3.7	9,407
Erect girth (circumference)	11.66 cm	4.6	381

From Veale and colleagues (2015), a review of studies in which a health professional measured each man with a standard procedure. Samples of men with a penis condition, previous surgery, erection problems or a complaint of small size were left out. Inches are converted from centimetres and rounded.

Notice how few men were measured erect: 692, against more than 10,000 soft. The authors list this as a limitation: relatively few erect measurements were taken in a clinical setting.

The two later reviews:

• Belladelli and colleagues (2023) pooled 75 studies with data from 55,761 men, published between 1942 and 2021, and counted only measurements taken by an investigator. Their averages were 8.70 cm soft, 12.93 cm stretched and 13.93 cm erect.
• King (2021) combined 10 studies in which researchers measured erect penises: the mean was 5.36 inches (13.61 cm) across 1,629 men. King concluded that the average erect length is between 5.1 and 5.5 inches (12.95 to 13.97 cm), and probably towards the lower end once volunteer bias is taken into account.

What is the average penis size in the UK?

A UK study set up to establish a reference range measured 609 men at hospital urology departments in Edinburgh and Livingston, Scotland. The average soft length was 8.7 cm (about 3.4 inches) hanging, and 14.3 cm (5.6 inches) stretched. The study didn't measure erect length.

Khan and colleagues published it in 2012 to give urologists a UK reference range. They used a rigid metric ruler on men aged 16 to 90 having routine examinations in clinics or in operating theatres. Worth knowing about the men: they were hospital patients, and the title describes them as Caucasian British men.

For European studies as a whole, the 2023 review found an average erect length of 14.12 cm.

Is 6 inches small or big?

Above the overall measured averages. Six inches (15.24 cm) compares with 13.12 cm in the 2015 review, 13.61 cm in King's review and 13.93 cm in the 2023 review, and King puts the average between 5.1 and 5.5 inches erect. Seven inches (17.8 cm) is above every erect-length average these reviews report, including the highest regional one (15.71 cm, from a single study in Australia), so it sits even further from the averages.

Average penis size by age: does it change?

In adult men, age seems to make little difference. The UK study of men aged 16 to 90 found no significant link between penile length and age. A study of 778 men attending urology clinics in Saudi Arabia, whose erections were brought on by an injection, found only a weak link, with erect length slightly lower in older men.

The 2023 review included only men aged 17 or over. The penis continues to grow through puberty, as that review notes, so adult averages don't apply to teenagers.

Average penis size by country: do the rankings hold up?

Measured size does vary by region, but nobody knows why, and the studies say little about individual countries. The 2023 review found that all measurements varied by geographic region: average erect length ranged from 11.74 cm in studies from Asia to 15.71 cm in the single study from Oceania (Australia).

The authors add that the cause of these differences is unknown, that the variations may lessen as migration continues, and that they couldn't look at finer differences because most studies didn't give precise information. They also say self-reported lengths should be regarded with caution, so a league table built on self-measurement deserves the same caution.

Has the average penis got bigger?

Measured erect length seems to have increased. After adjusting for region, age and the kind of men studied, the 2023 review found that average erect length rose 24% over 29 years. Soft and stretched lengths showed no such trend, and the authors say the cause is uncertain and should be investigated.

How to measure your penis the way studies do

Measurement techniques were similar across studies, the 2023 review says, though slight variations could contribute to differences. Some studies measure from the pubic bone rather than from the skin.

1. Use a rigid ruler. The UK study used a rigid metric ruler.
2. Measure along the top. The 2023 review counted length measured from the root of the penis to the tip of the head, along the top surface.
3. Allow for fat at the base. Some studies measure from the pubic bone: in the Saudi study, erect length measured from the pubic bone averaged 14.34 cm, against 12.53 cm from the skin, and the authors stress allowing for fat getting in the way of the measurement.
4. Measure girth around the shaft. Girth is the circumference: the Saudi study's average erect shaft circumference was 11.50 cm.

Expect some variation. The 2023 review notes that temperature, arousal, body size and the person measuring may all affect the result.

Does penis size matter?

The research is mixed. In a 2015 study, 75 women in California chose from 33 three-dimensional models, and the researchers concluded that women prefer penises only slightly larger than average, though for some women size had mattered.

The 60 women who named a preference chose an erect length of 6.3 inches (16.0 cm) and a girth of 4.8 inches (12.2 cm) for a long-term partner, and slightly more for a one-time partner.

The same study found that 27% of the women had ended a relationship partly because of a mismatch between their preference and their partner's size, and more of them named a penis that was too small than too large. Its limits, as the authors list them: the models were simplified blue plastic shapes, the women were recruited largely near a college campus, 15 of the 75 chose not to name a preference, and the answers were self-reported. The models were also built around an American estimate of 6 inches for the average erect length, above the measured averages on this page.

The authors also point to earlier research in which men thought women would find a longer penis ideal than the women actually did. King notes that studies show a majority of men wish they were larger. A 2007 review by Wylie and Eardley, led from a Sheffield clinic, describes worry about size as often within the normal experience of many men. Such concerns, they write, might be a sign of social anxiety or another problem such as erectile dysfunction, and excessive worry might present as body dysmorphic disorder.

What size is a micro penis?

A micropenis is a medical diagnosis, considered when a correctly measured stretched length is more than 2.5 standard deviations below the average for the person's age, in someone whose genitals are otherwise normal. A 2013 review describes it as a diagnosis often made incorrectly.

It's rare: the same review reports 1.5 in 10,000 boys born in the US between 1997 and 2000. Only a doctor measuring correctly can diagnose it.

Can you increase penis size?

The evidence for enlargement methods is poor. A 2020 systematic review, led from London and Turin, looked at 17 studies of men without penis problems who wanted to be bigger, covering 1,192 men screened, and found scant, low-quality evidence.

• Stretching devices (extenders) increased soft length, but by less than 2 cm.
• Injectables increased girth but were associated with a high complication rate.
• Vacuum devices didn't increase size.
• Some men reported a significant size increase, but complications were not infrequent, and none of the techniques was externally validated.

The reviewers found that counselling worked when it was offered: most men came to understand that their penis was normal and didn't want further treatment. They say injections and surgery should remain a last option, considered unethical outside clinical trials. King adds that the American Urological Association considers penis-lengthening surgery risky, and that most men seeking it have normal-sized penises.

For more questions like this, see our hub of men's sex questions, answered, or read what the research says about circumcision.

When to see a GP

The NHS notes that penises vary a lot in size and shape, and that there may naturally be a slight curve when erect. On its page about Peyronie's disease, a condition that makes the penis curve and can also shorten it, the NHS says to see a GP if:

• you have swelling or a hard lump on your penis
• your penis curves upwards or downwards when it's erect
• you have painful erections, or problems getting or keeping an erection, which make having sex difficult

Erection problems that keep happening are worth a check too: you can see a GP or go to a sexual health clinic. Our guide to erectile dysfunction covers the common causes.

The NHS lists worrying a lot about a specific area of your body, such as your penis, and spending a lot of time comparing your looks with other people's among the signs of body dysmorphic disorder (BDD), and says to see a GP if you think you might have it. Its symptoms can get better with treatment, and you can also refer yourself to an NHS talking therapies service.