Learn How to Reassure Your Teen Son About Concerns Over Penis Length

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Parents (and their sons) often have questions about puberty and what is a normal penis size. How do you know what is normal and that your son's penis growth is average? Is there something wrong if it's too small?

Normal Penis Size and Development

The good news is that penis size is rarely a medical problem. The bad news is that there are few answers about "normal" penis size that will satisfy a curious teenage boy. There always seems to be pressure to be bigger, and boys often think that they are smaller than average.

A teen boy's genitalia (penis and scrotum) develop in somewhat predictable stages. A boy's scrotum won't begin to enlarge until he is at least 9 years old. A penis can sometimes begin to lengthen at around 9 years old, but won't usually begin to lengthen until 10 years old.

If your son is concerned that his penis hasn't started to grow yet, don't worry. Sometimes a penis won't begin to get longer until the teen is 14 years old. If there is no change by the time he is 14 years old, a trip to the doctor may be necessary. Your pediatrician or family healthcare provider can let you know if your son's development is normal or not.

Average Length By Age

These measurements are taken from a table in the textbook "Adolescent Health Care: A Practical Guide." These are approximate ranges of flaccid or non-erect (soft) penises.

  • Age 10 to 11: 1.6 inches (4 centimeters) to 3.1 inches (8 centimeters)
  • Age 12: 2.0 inches (5 centimeters) to 4.0 inches (10 centimeters)
  • Age 13: 2.0 inches (5 centimeters) to 4.7 inches (12 centimeters)
  • Age 14: 2.4 inches (6 centimeters) to 5.5 inches (14 centimeters)
  • Age 15: 3.1 inches (8 centimeters) to 5.9 inches (15 centimeters)
  • Age 16: 3.9 inches (10 centimeters) to 5.9 inches (15 centimeters)
  • Age 17: 3.9 inches (10 centimeters) to 6.3 inches (16 centimeters)
  • Age 18: 4.3 inches (11 centimeters) to 6.7 inches (17 centimeters)

How Penis Size Is Measured

Measuring penis size is a tricky thing and is affected by many factors. Unless you are measuring the penis the same way a researcher did, it can cause a lot of confusion, so take these numbers with a grain of salt. In other words, your son may be measuring himself in a way very different from how a researcher does it, so these numbers are only a guide. 

Researchers often measure the stretched penis length of a flaccid penis. The penis is measured by pressing the fat down at the base of the penis and measuring from there (very close to the body) to the tip of the penis. This may also be done on the dorsal side of the penis, which is the underside of the penis that lies closest to the body when standing.

A Word From Verywell

If there is a question or concern about your son's body or development, contact your pediatrician. Penis size is rarely a medical concern. Your job as a parent is to reassure your son that he is growing and developing normally and that his body is fine just the way it is.

View Article Sources
  • Neinstein LS, Katzman DK. Neinsteins Adolescent and Young Adult Health Care: a Practical Guide. Philadelphia: Wolters Kluwer; 2016.