Penis fact vs fiction – from fractures to shrinkage and ‘REM erections’ – everything you need to know

THERE are some body parts which people focus on more than others, and penises are a good example of this.

The penis is involved with sexual intercourse and masturbation, obviously.

You might be too embarrassed to ask certain questions about your penis, like why it’s vaguely mushroom shaped or whether ‘wet dreams’ are normal past your teens

GP and author Dr Philippa Kaye sifts through penis facts and fiction

But in society, there can be a blurring between the penis and virility and masculinity and even power, much of which may not be the case!

Though penises are the subject of much contemplation, certain myths around them reign rampant – from shoe size reflecting the size of your member, to creams and oils being able to make it larger.

On top of this, it can often feel taboo or embarrassing to ask questions about your private parts.

From evolutionary explanations about why penises can look like mushrooms, to whether they can get smaller as you age and if it’s possible to break this prized body part – I answer questions about penises you’re too afraid to ask and sift through fact and fiction.

1. What is the average penis size?

The average size of a penis is approximately 9cm when flaccid/soft and about 13cm when erect. 

A micropenis is defined as a penis measuring less than 7cm.

If you have a micropenis, you can get treatment for it on the NHS.

But this is just the length of the penis on the outside – you might not know it, but there is around the same length of penile tissue inside as on the outside, extending into the pelvis.

There is often a lot of talk about penis size and an idea that size matters, but in terms of a heterosexual, male-female sexual relationship, how much the size of a penis matters varies between the partners.

One study reported that 45 per cent of men are not satisfied with the size of their penis, yet 85 per cent of the women surveyed were actually satisfied with their partner’s size.

In that study the size seemed to matter more to men than to women, perhaps because the majority of women do not reach orgasm by penetration alone but need external clitoral stimulation.

2. Does your shoe size reflect your penis size?

No. 

A study looking at the penises of over 100 men of varying ages looked at shoe size and penis length and found no correlation between the two.

3. Why is the penis shaped like a mushroom?

Penises come in all shapes and sizes.

From an evolutionary point of view, it’s perhaps obvious that the shaft of the penis is cylindrical or tube-like in shape, so that it can fit inside the muscular tube of the vagina. 

But why the shape of the glans, or head, of the penis? 

The glans penis is covered by the foreskin, unless it is removed in circumcision, which rolls back during an erection exposing the head.

So, there is a ridge between the top of the shaft of the penis and the glans, which is shaped rather like a mushroom.

One theory as to why this is is known as the ‘semen displacement theory’, which suggests that the shape of this ridge essentially scoops out and removes any sperm left behind in the vagina by a previous partner, who might be a genetic rival evolution-wise.

The theory was even tested in the lab.

A solution was made of starch and water to give a similar consistency to semen and was inserted into a tube-like device to represent the vagina.

A mushroom shaped ‘penis’ scooped out 90 per cent of this solution with just one thrust, compared to a device without the ridge between the shaft and head, which only removed 35 per cent!

4. Can you break your penis?

There are no bones in the penis, but you can still break it.

During an erection there are spongy tissues called corpus cavernosum, which fill with blood to make the penis erect. 

If there is a trauma, often a violent twisting or bending motion when the penis is erect, then part of the covering of the corpus cavernosum called the tunica abulginea can burst, leading to bleeding into the penis and a very painful swelling.

It is rare and tends to occur during sex, often when a partner is on top.

5. Can penises point in any direction?

Yes.

When the penis is erect it can point in any direction, from directly up to forward pointing, to downwards, as was found in a study involving almost 1500 men.

Added to this, it is normal for penises to have a slight curve, in either direction.

In fact, a curve between 5 and 30 degrees is considered healthy and normal. If though the curve is more extreme, causing pain or difficulties with erections or sex, please seek medical advice. 

6. Can your penis get smaller?

Yes, your penis can shrink.

There are lots of causes of this, included high blood pressure and peripheral vascular disease, which may lead to decreased blood flow to the penis.

Low testosterone levels and ageing may also affect the size of the penis, as can having a significant curve due to Peyronie’s disease. 

Some types of treatment for prostate cancer, such as a radical prostatectomy, can affect the size of the penis.  

7. Are multiple erections during the night normal?

You may think of wet dreams as being associated with puberty, but actually the average healthy male has three to five erections each night, with the ‘morning glory’ being the last of these.

They seem most likely to occur in rapid eye movement (REM) sleep, but the cause is not known.

Each erection at night can last about 25 to 30 minutes, amounting to around two hours of erections during the night.

8. ‘Showers’ or ‘growers’?

The size of your penis when flaccid does not necessarily predict the size when erect, as small penises are more likely to increase proportionally more in length than longer ones.

A study from the 1980s showed that, on average, longer penises increased by just under 50 per cent from flaccid to erect, while shorter penises increased by almost 90 per cent. 

And when penises are erect there is less variation in length – flaccid penises vary in length by about 3cm, but only by about 1.7cm when erect.

A more recent study from 2023 found that about 25 per cent of men could be considered ‘growers’ and 25 per cent ‘showers’ – but most fell into a “grey zone” in between the two categories.

9. Creams and oils can make your penis bigger?

No they can’t.

The only proven ways to increase the size of your penis is by surgery, which can increase length and girth.

Surgery to increase the length of your penis involves cutting a ligament which attaches the penis to the pelvis, but this only affects the length of the penis when it is flaccid.

Surgical treatments to increase girth can involve a fat transplant or use of an implant.

These are generally only available on the NHS if you have a micropenis.