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. Back to Articles Related Articles Male Reproductive System What makes up a guy's reproductive system and how does it develop? Find the answers to these questions and more. Read More How to Do a Testicular Self-Exam (Slideshow) The testicular self-examination (TSE) is an easy way for guys to check their own testicles to make sure there aren't any unusual lumps or bumps - which are usually the first sign of testicular cancer. Read More Why Does the Doctor Have to Examine My Testicles? Find out what the experts have to say. Read More I Have Bumps On My Penis. Is This Normal? Find out what the experts have to say. Read More Testicular Exams If you're a guy, you may be wondering why the doctor needs to do a testicular exam. Find out in this article. Read More Is It Normal for One Testicle to Be Bigger? Find out what the experts have to say. Read More Varicocele A varicocele is an enlargement of the veins in the scrotum. Although there is no way to prevent a varicocele, it usually needs no special treatment. Read More Is It Normal to Get Erections? If you've ever had an erection in an embarrassing situation, you've probably asked yourself this question. But erections are a perfectly normal function of the male body, especially in guys who are going through puberty. Read More Gynecomastia Puberty can be confusing, especially when unexpected changes happen. Learn what gynecomastia is and why it happens. Read More What Are Wet Dreams? Find out what the experts have to say. Read More Everything You Wanted to Know About Puberty Voice cracking? Clothes don't fit? Puberty can be a confusing time, but learning about it doesn't have to be. Read all about it. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.