What is the normal size of a testicle (testis) in an adult male?

Normal Testicular Size in Adult Males

The normal testicular volume in adult males ranges from 12-25 ml, with an average of approximately 13.6 ml. 1

Measurement Methods

• Prader orchidometer is a good surrogate for testicular volume measurement and is easier to perform and more cost-effective than ultrasound in clinical practice 2
• Ultrasound measurement provides the highest degree of accuracy and reproducibility and is considered the standard for quantitation of testicular volume 3
• Clinical methods (ruler, calipers, orchidometers) tend to overestimate testicular volume by 70-80% in adults compared to ultrasound measurements, mainly due to inclusion of scrotal skin and epididymis 3

Normal Values

• Mean testicular volume in healthy adult males is approximately 13.64 ± 3.44 ml based on ultrasound measurements 1
• There is typically a small but statistically significant difference between left and right testicular volumes:
  • Left testis: 13.94 ± 3.72 ml
  • Right testis: 13.34 ± 3.61 ml 1
• Testicular volumes less than 12 ml are generally considered small or atrophic 2

Clinical Significance of Testicular Size

• Testicular size has a direct correlation with testicular function and can be helpful in rapidly assessing andrological status during physical examination 4
• Mean testicular size strongly correlates with:
  • Serum follicle-stimulating hormone (FSH) levels
  • Total sperm count and sperm concentration
  • Sperm motility and morphology 4
• Testicular volume is negatively correlated with luteinizing hormone (LH) and FSH, and positively correlated with testosterone levels 1
• Sperm quantity and quality are both impaired in testes smaller than 14 ml 4

Factors Affecting Testicular Size

• Testicular size is generally independent of age in adult males and smoking habits 1
• Conditions associated with smaller testicular volumes include:
  • Hypogonadism 1
  • Unexplained infertility 1
  • History of cryptorchidism (undescended testicles) 2
  • Previous childhood cancer treatment (especially leukemia, cranial/testicular irradiation, and cyclophosphamide therapy) 5

Clinical Implications

• Small testicular size (<12 ml) may warrant further investigation, especially when associated with:
  • Infertility concerns 2
  • History of undescended testicles 2
  • Suspected hypogonadism 1
• Testicular ultrasound is recommended in selected cases such as:
  • Large hydrocele
  • Inguinal testis
  • Epididymal enlargement/fibrosis
  • Thickened scrotal skin
  • Small testis with large epididymis 2

Measurement Pitfalls

• External measurements with calipers typically overestimate testicular dimensions compared to ultrasound:
  • Length by approximately 5.7 mm
  • Thickness by approximately 2.9 mm
  • Width by approximately 1.4 mm 6
• When using external measurements, it's important to account for the thickness of scrotal skin and testicular coats 6