What is the normal size of adult human testicles in a healthy male with no medical history?

Normal Adult Testicular Size

In healthy adult males with no medical history, normal testicular volume ranges from 15-25 ml (approximately 4-5 cm in length), with volumes below 12 ml considered atrophic and associated with impaired spermatogenesis. 1

Standard Measurement Parameters

Volume-Based Assessment

• The lower limit of normal testicular volume is approximately 12 ml, below which testes are considered small or atrophic and warrant further investigation 2, 1
• Normal adult testicular volume typically ranges from 15-25 ml, which corresponds to the size comparisons mentioned (large olive to small plum) 1
• The American Urological Association suggests that a testicular volume of 12 ml represents the lower limit of normal, with 4 cm testicular length corresponding to approximately 15-18 ml volume 1

Length-Based Measurements

• Normal adult testicular length in Japan is greater than 14 ml (measured by orchidometer), while in the United States it is greater than 17 ml 3
• A 4 cm testicular length corresponds to a volume of approximately 15-18 ml, which falls within the normal range 1

Clinical Measurement Methods

Orchidometer Assessment

• The Prader orchidometer is the gold standard for clinical testicular volume measurement, providing a good surrogate for ultrasound volume while being easier to perform and more cost-effective 1
• The orchidometer consists of a graded series of elliptical models with volumes indicated, allowing rapid bedside assessment 3

Ultrasound Calculation

• When using ultrasound, the Lambert formula (Length × Width × Height × 0.71) provides the most accurate volume estimates compared to the traditional ellipsoid formula 1
• The traditional ellipsoid formula (0.52 coefficient) systematically underestimates testicular volume by 20-30% and should not be used for clinical decision-making 1

Clinical Significance of Size

Correlation with Function

• Mean testicular size strongly correlates with total sperm count and sperm concentration, with the strongest correlation being with serum FSH levels 1, 4
• Testicular volumes less than 12 ml are associated with impaired spermatogenesis, higher risk of intratubular germ cell neoplasia, and potential infertility 1

Size Discrepancy

• A size discrepancy between testes greater than 2 ml or 20% warrants ultrasound evaluation to exclude pathology, regardless of absolute volume 1

Common Pitfalls

Measurement Errors

• High-frequency probes (>10 MHz) should be used for ultrasound measurement to maximize resolution and accurate caliper placement 1
• Incorrect caliper placement during ultrasound can lead to severely underestimated volumes and misdiagnosis of testicular atrophy 1
• The same sonographer should perform serial measurements when possible to minimize inter-scan variability 1

Clinical Context Matters

• Testicular volume alone cannot definitively predict fertility status—even "normal-sized" testes should prompt semen analysis in the context of infertility 1
• True biological change in testicular size over 4 weeks is extremely unlikely in adults unless there is acute pathology 1