A healthy adult testicle typically measures between 15 mL and 35 mL in volume, or roughly half an inch to 1.5 inches wide. There’s a wide range of normal, and most men fall somewhere in the middle. What matters more than hitting an exact number is whether your testicles have stayed consistent over time and whether both are in a similar range.
Normal Size Range for Adults
Each testicle is roughly the size of a small plum or a large olive. In clinical terms, 15 to 35 mL covers the normal adult range, with most men landing around 20 mL per testicle. Doctors measure testicular volume using a tool called an orchidometer, which is essentially a string of numbered beads in graduated sizes. The clinician holds each bead up to the testicle and finds the closest match. In practice, most people will never need this kind of measurement unless a size concern comes up during a physical.
It’s completely normal for one testicle to be slightly larger than the other. Clinically, a difference of less than 4 mL between the two sides is considered symmetric. The left testicle also tends to hang a bit lower than the right in most men. None of this signals a problem.
How Testicles Grow During Puberty
Testicles are one of the first things to change when puberty starts, often before height or voice changes become noticeable. Doctors track this progression through five stages of sexual maturity.
- Before puberty: Each testicle is 1.5 mL or smaller, about the size of a pea.
- Early puberty (roughly ages 9 to 11): Volume increases to about 1.6 to 6 mL. The scrotal skin thins and begins to hang lower.
- Mid-puberty: Testicles reach 6 to 12 mL, and the penis starts to lengthen.
- Late puberty: Volume climbs to 12 to 20 mL as the penis also grows in width.
- Adult stage: Testicles reach 20 mL or more, with adult appearance of the genitals overall.
This progression usually unfolds over about four to five years. Reaching the adult stage later than peers is common and not automatically a concern, but testicles that remain very small (under 6 mL) into late adolescence can be a sign of a hormonal issue worth investigating.
When Small Testicles May Signal a Problem
Testicles under 6 mL in an adult are considered very small and can be a sign of low testosterone production. At that size, a doctor will typically check hormone levels and may order genetic testing to rule out conditions like Klinefelter syndrome, a chromosomal variation that affects roughly 1 in 600 men and often goes undiagnosed until fertility problems arise.
A gradual decrease in size over time can also indicate a problem. Testicles can shrink from varicoceles (enlarged veins in the scrotum), prolonged use of anabolic steroids, or certain infections. If you notice that one or both testicles feel noticeably smaller than they used to, that’s worth bringing up with a doctor even if there’s no pain.
Size and Fertility
Testicle size has a direct relationship with sperm production because the vast majority of testicular tissue is dedicated to making sperm. Larger testicles generally produce more sperm, though size alone doesn’t determine fertility.
Research on this connection has identified some useful benchmarks. When total testicular volume (both sides combined) drops below about 29.5 mL, the odds of an abnormal sperm count increase more than sixfold. A size difference of greater than 20% between the two testicles has also been linked to significantly lower sperm counts. These findings come from studies of men with varicoceles, so they may not apply perfectly to the general population, but they illustrate how much testicular volume matters for reproductive function.
For men trying to conceive, a physical exam that includes testicular measurement is a routine part of a fertility workup. It’s a quick, painless assessment that can flag potential issues before more involved testing.
How to Check Your Own Testicles
You can’t precisely measure your testicular volume at home without an orchidometer, but regular self-exams help you learn what’s normal for your body so you’ll notice changes early. The Mayo Clinic recommends doing this during or after a warm shower, when the scrotal skin is relaxed.
Stand unclothed in front of a mirror. Hold your penis out of the way and look at the scrotum for any visible swelling. Then examine each testicle individually: place your index and middle fingers underneath and your thumbs on top, and gently roll the testicle between them. You’re feeling for hard lumps, smooth rounded bumps, or any change in size, shape, or firmness compared to what you’re used to. A soft, slightly spongy tube along the back of each testicle is the epididymis, which is normal anatomy.
What you’re watching for isn’t a specific measurement but change over time. A testicle that suddenly feels larger, harder, or heavier than it did a few months ago deserves medical attention. The same goes for sudden swelling paired with pain, nausea, fever, or blood in urine or semen. Testicular torsion, where the testicle twists on its blood supply, causes severe pain and swelling and requires emergency treatment within hours to save the testicle.