Normal Testicular Size on Self-Examination
A normal adult testicle should feel approximately 3.5-5 cm in length (roughly the size of a small plum or walnut), corresponding to a volume greater than 12-15 mL, with anything below 12 mL considered small or atrophic and requiring medical evaluation. 1
What to Expect When Palpating Your Testicles
Normal Size Parameters
- Length: The normal adult testicle measures 3.5-5 cm in length when palpated 1
- Volume: Normal testicular volume is greater than 14 mL in Japanese populations and greater than 17 mL in American populations 1, 2
- Critical threshold: Volumes below 12 mL are universally considered pathologically small or atrophic and warrant medical investigation 1, 3
Expected Asymmetry
- The right testicle is typically slightly larger than the left - this is completely normal 4, 5
- In healthy adolescents and adults, approximately 59% have a smaller left testis 4
- Size differences up to 2 mL or 20% between testicles can be normal, but larger discrepancies warrant ultrasound evaluation 3, 1
When Size Becomes Concerning
Red Flags Requiring Medical Evaluation
- Testicles that feel smaller than 3.5 cm in length or appear significantly smaller than a walnut 1
- Sudden change in size - particularly rapid shrinkage or atrophy 6
- Marked asymmetry where one testicle is more than 20% smaller than the other or differs by more than 2 mL 3, 4
- Hard lumps or masses that feel different from the normal firm, smooth texture 7
High-Risk Scenarios
- Age under 30-40 years with small testicles (volume <12 mL) carries a greater than 34% risk of intratubular germ cell neoplasia if testicular cancer develops 3, 1
- History of undescended testicles (cryptorchidism) substantially increases cancer risk and mandates closer surveillance 3, 1
- Small testicular size strongly correlates with reduced sperm count and impaired fertility 8, 5
Clinical Context
Why Size Matters
- Testicular volume directly correlates with sperm production - mean testicular size has the strongest correlation with total sperm count and sperm concentration 8
- Testes smaller than 14 mL show impairment in both sperm quantity and quality 8
- Volumes below 12 mL are associated with significantly impaired spermatogenesis and potential infertility 3, 1
Common Pitfall to Avoid
- Don't panic if you notice slight asymmetry - one out of five healthy adolescents has a smaller left testis that meets threshold values sometimes used in medical management 4
- However, if you notice progressive shrinkage or new asymmetry developing over time, seek medical evaluation 6
What to Do If Concerned
Perform monthly testicular self-examination to detect any changes early, particularly if you have risk factors like history of undescended testicles or family history of testicular cancer 6, 1. If your testicles feel smaller than a walnut (approximately 3.5 cm), have developed new asymmetry, or you notice any hard lumps, obtain medical evaluation with physical examination and potentially scrotal ultrasound 3, 1.