In the last few years, it has become apparent that the average man's penis is not as long as had been thought previously.
For decades, medical books and articles in the press have confidently stated that penile length is generally about 6.5 inches (16.5 centimetres).
As a result, a lot of males who are slightly shorter than this have felt rather inadequate.
However, it now seems that the statistics on which this 'average' was based could well have a serious flaw. It is this: the figure was originally calculated by collecting measurements that men had carried out themselves!
Self-measurement of this sort is notoriously unreliable.
Why? Because so many males don't know where to measure from or use inaccurate rulers or ancient tape measures.
Also, there's probably a tendency for guys to round their 'scores' upwards, in an attempt to make themselves sound better-endowed. And the results tend to be skewed by people who falsely claim to be 10 or 11 inches long.
In recent times, a number of scientists have attempted to obtain more reliable figures, by the simple expedient of employing a trained person to carry out the measurement of each man.
And the results, which they have produced, seem to indicate that the average adult male is considerably shorter than had been thought.
In reality, the mean length of the erect penis appears to be only about 5.88 inches (14.9 centimetres), which is considerably less than the 'old' measurement.
Does all this matter?
If you're a woman, you probably think that this concern about fractions of an inch is rather silly.
But if you're a man, you will know that such matters are – somewhat irrationally – of considerable importance to many males.
Why do men worry about length?
Even in this supposedly enlightened century, men fret about penis size and especially length.
Though the vast majority of guys have more than enough bulk and length to perform well as lovers, there's a widespread masculine obsession that 'more would be better'. So, we get a constant flow of emails and letters from males who are worried that they are 'too small'.
Companies who advertise penis-enlarging creams and pills on the internet make vast sums of money by exploiting this obsession. But other than surgery, there's nothing that's clinically proven to increase penis size.
Any woman reading this article may find it puzzling that so many men are concerned about the length of their penis and wish they had 'just a couple of inches more'. But that's the way that a lot of men are.
Size matters
To the average man, his penis is, consciously or unconsciously, one of the most important things in the whole world. At an early age he discovers it and immediately becomes fascinated by it.
But then a note of uncertainty enters his mind: 'Isn't mine rather small?' Look at Dad's, look at big brother's, look at those in the men's changing room – and he asks himself if he will ever be as big as that.
And so he goes on through life, always a tiny bit sensitive about the size of his organ, always convinced that it would be nicer if it were just that little bit longer.
No matter how often it's written that penile size doesn't matter, and that women aren't attracted to a man because of the length of his organ, many males continues to think the same way.
The average female cannot understand this obsession with penile measurement. So if you're a woman, never belittle a man's penis in bed, even as a joke, or say anything to indicate that you think it's small. The guy may take you seriously, and if he does, he'll be deeply hurt.
We have known men who have gone on to have problems with impotence (erectile dysfunction) after someone made an unthinking remark about their dimensions. But almost all of these men had a perfectly normal male organ. Each one just thought he was very small compared with other guys.
It is also worth noting two points about women.
Some women really dislike the idea of a large penis and may be frightened by one that is too long.
Some women are much more impressed by the thickness of a penis, rather than its length. This is because some females like the sense of feeling stretched round the entrance to the vagina – so if a guy is quite broad at the base of his penis, this can feel very exciting and satisfying to such women.
A question of perspective
The trouble is that every man sees his own penis in a foreshortened view. The angle at which you look down inevitably makes your penis seem shorter than it is.
But when you glance at another man's organ, there's no such foreshortening effect, so very often it'll look as though the other guy is slightly better endowed.
A lifetime of comparison of this sort (and virtually every male does a quick mental check on each naked man he sees) can easily make you feel a bit inadequate. But it's important to realise the facts about penis length.
Average penis length
Measuring the penis when it isn't erect is pointless, since the length and bulk are affected by various temporary factors, such as the ambient temperature. Even the largest male organ can shrink to virtually nothing if the man goes for a swim in cold water.
However, at normal temperatures a non-erect penis usually measures between 8.5cm and 10.5cm (3-4 inches) from tip to base.
The average figure is about 9.5cm (3.75 inches).
Of course, it's true that some men have big penises and some have smaller ones, just as some men have small feet and some have big feet, but the measurement is not – repeat not – an index of virility.
Most people think that a tall man will usually have a large penis, but this is not entirely true. The distinguished American researchers Masters and Johnson measured the penile lengths of more than 300 men.
The longest organ was 14 cm (5.5 inches) in the flaccid state. It belonged to a slim man who was 5' 7" tall (170 cm).
The shortest penis measured 6cm (2.25 inches). It belonged to a fairly heavily built man of 5' 11" (180cm).
It's also worth pointing out that there is no correlation between penile size and race.
Average size of erections
We've talked about the length of the penis in its ordinary non-erect state, but how long is it be when it's erect?
Interestingly, most penises are very much the same size when erect.
The man whose non-erect penis is smallish will usually achieve about a 100 per cent increase in length during sexual excitement.
The man whose non-erect penis is on the largish size will probably manage about a 75 per cent increase.
So you can see that even if a man has got a 'small' penis, he's got a built-in compensating factor that will bring him up to about the same size as the guy who appears to be 'better equipped' in the shower room.
As we've already said, the average penis is now known to be appreciably shorter than was traditionally thought. Most authorities now say that the mean length of the erect male organ is between 5.1 inches (12.9 centimetres) and 5.9 inches (15 centimetres).
One of the most accurate and scientific pieces of research on this subject was carried out in Mexico behalf of LifeStyles condoms. Under the supervision of a doctor, four trained health professionals measured the erect penises of 300 men (who were mostly young Americans).
They found that the average length was 5.877 inches (14.93 centimetres) – far less than the figure which had been generally quoted in the past.
A review published in the British Journal of Urology in 2007 broadly confirmed this finding.