Just about every guy wonders how he measures up "down-there." Here's the lowdown for any guy who's ever worried about whether his penis is a normal size.

There is a wide range of normal penis sizes. Although you may see guys with penises that are bigger or smaller than yours, it is very likely that your penis is a normal size. Penis size is determined by your genes , just like eye color or foot size. And there's a lot less difference in penis size between guys when they get an erection than when their penises are relaxed.

Despite what you may hear or read, no special exercises, supplements, or diets will change a guy's penis size.

The penis grows the most during puberty. Some boys start puberty around 9 and others don't start until they are 15. Usually by the end of puberty, a guy's penis has reached its expected size. Puberty usually ends about 4 years after it starts, so this is usually around age 13–19.

In addition to size, guys also wonder about how their penis looks. For example, a guy might wonder if the skin covering the penis is normal or if it's OK for a guy's penis to hang to the left or right (it is!).

If you're concerned about how your penis looks, ask your doctor. Teen guys should have testicular exams every year at their regular checkup. So that's a good time to ask your doctor any questions.