The fear that your penis looks too small or is too small to satisfy your partner during sex is common. But studies have shown that most men who think their penises are too small actually have normal-sized penis. Similarly, studies suggest that many men have an exaggerated idea of what constitutes "normal" penis size. The length of a non-erect penis doesn't consistently predict length when the penis is erect. If your penis is about 13 cm (5 inches) or longer when erect, it's of normal size. A penis is considered abnormally small only if it measures less than 3 inches (about 7.5 centimeters) when erect, a condition called micropenis.