So what is the average penis size?

A non-erect penis usually measures between 6cm and 10.cm (2.5-4 inches) from tip to base.

The average figure is about 9.5cm (3.75 inches), but this kind of precise measurement is rather valueless. Many factors can cause a temporary shrinkage of two inches or more, for instance cold weather or going swimming, so you needn't worry if you happen to fall short of the average figure.

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 largest 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 smallest 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.

And how long should 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.
• This means the great majority of penises measure between 15cm and 18cm (6-7 inches) when erect, with the average figure being about 16.5cm (6.5 inches).

So 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.

Sex and women

Virtually every man forgets that it doesn't matter how long or how short your penis is, because the vagina will accommodate itself to any length.

• The vagina of a woman who hasn't had a child is only 7.5cm (3 inches) long when she's not sexually excited. The figures for women who have had babies are only slightly different.
• Even when aroused, a woman's vagina usually extends only to a length of about 10cm (4 inches).

This means any man's penis will fill her vagina completely, unless you happen to be one of those rare guys with an erect penile length of less than four inches.

You're probably now wondering how the average man with an erection of six inches manages to insert his penis into the vagina at all.

The vagina has the most remarkable capacity for lengthening if something is introduced into it gradually.

So the exceptional man whose erect penis is eight inches long can still make love to any woman, providing he excites her properly and introduces his organ very slowly. If he does this, her vagina will lengthen by 150 or 200 per cent to accommodate him. But don’t forget, it’s not quantity but quality that counts.

Is it normal to have a curved penis?

It’s common for the penis to curve slightly upwards or to the left or right when it’s erect.

However, if a bend in your penis is causing you problems, such as pain during sex, or you feel any abnormal lumps in your penis, see your GP or go to a local sexual health or GUM (genitourinary medicine) clinic.