Granite Male Enhancement The length of a non-erect penis doesn't reliably foresee length when the penis is erect. On the off chance that your penis is around 13 cm (5 inches) or longer when erect, it's of ordinary size. A penis is considered anomalous little just on the off chance that it quantifies under 3 inches (about 7.5 centimeters) when erect, a condition called micropenis.