Know that you get a distorted picture if during showering you glance down to check the others out. Your own penis looks smaller because you view it from above.
There is a negative correlation between the flaccid penis and the increase during an erection. A small penis normally adds more inches when it gets erect than a big one. So don’t jump to conclusions when you compare flaccid penises: what you see is not what you get.
An erect penis of about 3 inches is enough to have intercourse.
For intercourse girth is more important than length, because this determines the amount of friction between vagina and penis.