Testicles come in many different shapes and sizes. It is also common for one testicle to be slightly larger than the other and for one testicle to hang lower. Due to this extensive variability, there are several different ways to measure a person's testicles.

One measurement looks at volume, which averages about (cm³). Another way to assess testicle size is to measure the length from top to bottom. On average, this length is between 4.5 and 5.1 centimeters.

People with testicles much smaller than this may worry. However, if there are no accompanying symptoms, there is rarely a problem.

Rather than comparing their testicle size with that of other people, an individual should look at whether their testicles have changed over time. Testicles that are suddenly much smaller or larger than usual may signal a problem.

In this article, we examine the potential causes of small testicles and the treatment options. We also explain when a person with small testicles should get advice from a doctor.

a young man looking pensive as he thinks about his Small testicles
Low testosterone is one possible cause of small testicles.

A found that testicular volume, alongside body mass index (BMI), could be a predictor of testosterone levels. On average, the participants with lower testosterone had smaller testicles.

Many people with low testosterone levels have normal sized testicles, so it is important to look at all symptoms and not just testicle size.

Some symptoms of low testosterone include:

A varicocele is an enlarged swelling of the veins within the scrotum. While some people may notice pain or swelling, others may have no symptoms at all.

Some people with varicoceles have problems with fertility. About of males with infertility have varicoceles, although there are also males with varicoceles who do not have infertility.

Some individuals with a varicocele may notice that their testicles shrink or that one testicle is suddenly smaller than the other. They may also experience an aching pain deep in the scrotum.

Surgery can treat most varicoceles. In many cases, the testicles return to their usual size after surgery.

Testicular atrophy is when the testicles shrink. Several conditions can cause testicular atrophy.

One well-known cause of testicular atrophy is surgery to repair an inguinal hernia. This complication is rare, affecting only about of males who undergo primary inguinal hernia repair.

Individuals who have repeated inguinal hernia repairs have a higher risk of testicular atrophy, with about developing this complication.

Some other causes of testicular atrophy include:

A reduction in testicle size after testicular torsion may be a risk factor for testicular cancer. Anyone who notices that their testicles are suddenly smaller should see a doctor.

It can be difficult to distinguish the symptoms of testicular cancer from those of other types of cancer.

Some symptoms of testicular cancer include:

  • a lump on the testicles
  • an enlargement of the testicles
  • having fluid in the scrotum
  • enlarging breasts
  • a feeling of heaviness in the testicles or scrotum
  • a dull ache in the back or abdomen
  • experiencing shortness of breath

Some risk factors for testicular cancer include:

  • An undescended testicle (cryptorchidism). People with cryptorchidism are more likely to develop testicular cancer than those with descended testicles.
  • Family history. While most people with testicular cancer do not have a family history of the disease, having a first-degree relative with testicular cancer increases a person's risk.
  • HIV. People with HIV, particularly those with stage 3 HIV, have a higher chance of developing testicular cancer.
  • Previous testicular cancer. About of those who have received a diagnosis of cancer in one testicle will develop cancer in the other testicle.
  • Race and ethnicity. White males are more likely to develop testicular cancer than black and Asian American males.
  • Age. Although testicular cancer can affect males of any age, close to of testicular cancers occur in those between the ages of 20 and 34 years.