Fortunately condoms are not all the same size and shape.
condom too big - it may slip off or become damaged during intercourse
condom too small - it will be uncomfortable, and could split
condom not long enough to cover the whole penis - the collar of the condom may roll up or the condom could be be pulled off during intercourse.
Would my partner prefer a big penis?
We are built to enjoy sex, and generally speaking there are very few individuals whose dimensions prevent them from enjoying sex with their chosen partner. When men and women are asked what makes good sex, they rate tenderness, consideration and foreplay far above penis size.
How to Measure Penis Size:
With the penis erect, measure length and girth in millimeters as follows:
Length: measure along the top of the penis from the tip to the point where the penis joins the body. Girth - measure around the penis circumference (using a tape measure or a piece of string) at the widest point.
The following results are averaged from a number of independent tests carried out in several countries, all of which gave broadly the same results: The penis length is most commonly 150 to 160 mm, and the girth 130 to 140mm (which translates to 41-45mm width across the shaft).

Can I Increase the Size of my Penis?
This is supposedly possible, if you have a mind to do so, but is not without risk. Before you undertake any program of penis enhancement you would do well to read some personal experiences of what can happen.
Condom Sizes - The standard size for a condom is 98 to 106mm girth (un stretched), and 180mm long. This means that those with a girth of 120mm and below may find average condoms slip off too easily, Those with a length of over 180mm risk having the condom roll up or slip off inside their partner during sex, those with a girth of much above150mm may find condoms uncomfortably tight. With more than 1 in 3 of men fitting into one or more of these categories, it's no wonder that almost half of men felt that their condoms were a poor fit.
The above content was adapted from the following web site:
http://www.feelconfident.co.uk/condoms/size_chart.htm