How long does your penis have to be to hit the cervix?

Penile Anatomy. You may not like the answer. But, first, women's vaginas vary in length and width. Second, hitting the cervix is not usually the goal with intercourse, it is not the spot that leads to your female partner's orgasm. The average length of a man's erect penis in the United States is 4.5 inches. This means that 50% of men are smaller and 50% of men are larger than this.