Average Male Testicle Size
The average adult male testicular volume is approximately 15-18 ml, with volumes below 12 ml considered atrophic or abnormally small. 1
Normal Reference Values
Adult Males
- Normal testicular volume ranges from 15-18 ml per testis, which corresponds to a testicular length of approximately 4 cm 1
- The lower limit of normal is 12 ml, below which testes are classified as small or atrophic 2, 1
- Mean testicular volume in adult populations is approximately 13-14 ml when measured by ultrasound 3, 4
Measurement Context
- Right testis is typically slightly larger than left (median 14.1 ml vs 13.0 ml), though this difference is not clinically significant 4
- A size discrepancy greater than 2 ml or 20% between testes warrants further evaluation to exclude pathology 1
Clinical Significance of Testicular Size
Volumes Below 12 ml
Testicular volumes less than 12 ml are definitively considered atrophic and associated with significant pathology: 1
- Impaired spermatogenesis with oligozoospermia (low sperm density) 3, 5
- Elevated risk of intratubular germ cell neoplasia (TIN): In men under 30 years with volume <12 ml, there is a >34% risk of TIN in the contralateral testis if testicular cancer is present 2, 1
- Reduced fertility potential: Mean sperm density falls into oligozoospermic range when testicular volume is below 10 ml 3
- If TIN is untreated, invasive testicular tumor develops in 70% of cases within 7 years 2, 1
Correlation with Testicular Function
Testicular size strongly correlates with reproductive function: 5
- Strongest correlations exist between testicular size and serum FSH levels, total sperm count, and sperm concentration 5
- Significant correlations also exist with sperm motility, percentage of live sperm, and sperm morphology 5
- Both sperm quantity and quality are impaired in testes smaller than 14 ml 5
Measurement Methods
Ultrasound (Gold Standard)
- Volume calculated using the Lambert formula: Length × Width × Height × 0.71 1, 3
- High-frequency probes (>10 MHz) should be used to maximize resolution and accurate caliper placement 1
- Ultrasound provides more accurate measurements than physical examination methods 6
Prader Orchidometer
- Good surrogate for testicular volume measurement and is easier to perform and more cost-effective than ultrasound in clinical practice 1
- Orchidometer readings systematically underestimate volume compared to ultrasound (e.g., 15 ml by orchidometer corresponds to 16-18 ml by ultrasound) 1
External Caliper Measurements
- Systematically overestimate dimensions compared to ultrasound: length by 5.7 mm, thickness by 2.9 mm, and width by 1.4 mm 6
- Does not account for skin thickness, testicular coats, or epididymal head position 6
Age-Related Development
Pediatric Values
- Neonatal testicular volume: Mean 0.35 ml 6
- Intensive growth begins at age 10 years, with testicular volume increasing 10-fold from 1.36 ml at age 10 to 12.83 ml by age 17 6
- By age 13 years, testicular volume exceeds 3 ml in all boys 7
- Ages 16.5-18 years: Testicular volume ranges from 6-22 ml 7
Common Pitfalls
Measurement Errors
- Technical error in caliper placement during ultrasound can lead to severely incorrect volume calculations 1
- Proper measurement technique requires explicit attention to avoid misdiagnosis of testicular atrophy 1
Clinical Context Matters
- If a patient has normal fertility, no history of cryptorchidism, and normal secondary sexual characteristics, the likelihood of true severe testicular atrophy is low, suggesting measurement error if small volumes are reported 1
- History of cryptorchidism is associated with smaller average testicular volume (median 10.5 ml vs 14.1 ml in men with normal descent) 4