Average penis length (flaccid/not erect): from 3.4 inches to 3.7 inches (8.6 cm to 9.3 cm). Average penis length (erect): from 5.1 inches to 5.7 inches (12.9 cm to 14.5 cm). Average penis girth (circumference when erect): from 3.5 inches to 3.9 inches (8.8 cm to 10 cm). These numbers are obviously very different from the sizes we hear (and see) in adult movies, and even the kinds of numbers you read on line. Femaleâ€™s sexual satisfaction does not depend on penile length. It depends upon your love & affection for her, quality of intimate moments, warmth in relationship and lots of other nonsexual factors.