Average Length (not erect) = 3.4-3.7 inches
Average Length (erect) = 5.1-5.7 inches
Average girth (circumference when erect) = 3.5-3.9 inches
As my friend said that his girlfriend is not satisfied with their sexual life because of which there are regular fights between them, this is one more side of dissatisfied sex. If one of the partners are not satisfied with their sex life then that may lead to damage your emotional life and peace which ultimately harm you on your relation.
To avoid all this one should take prior steps so that he won't have to face such situation ever. Just analyse yourself on the basis of above information and see in which group you fit in. If penis size is the cause for your dissatisfied sex life then you have to hurry up and act accordingly. There are some herbal products like Sizeplus available in the market which help you to increase your penis size and maintain your sex life to its normal path.