Testicles are considered big when each one exceeds about 30 milliliters in volume, roughly the size of a large chicken egg. Most adult men fall well below that threshold, with about 80% having a testicular volume between 20 and 30 mL. The average, measured by ultrasound, is closer to 14 mL per testicle.
What Counts as Normal Size
Adult testicles typically measure between 14 and 30 mL each, with quite a bit of natural variation from person to person. A study of over 1,100 young men (ages 19 to 27) found the average volume was about 18 mL per testicle. That’s roughly the size of a small plum or a large olive.
It’s also normal for one testicle to be slightly larger than the other, or for one to hang a bit lower. These asymmetries don’t indicate a problem. What matters more than absolute size is whether your testicles have stayed relatively consistent over time and feel smooth and firm without hard lumps.
When Size Is Medically “Big”
The clinical term for abnormally large testicles is macroorchidism, defined as a testicular volume greater than 30 mL. At that point, a doctor would typically want to investigate the cause. The most well-known genetic link is Fragile X syndrome, a condition that affects brain development and commonly causes enlarged testicles after puberty. Macroorchidism is so closely associated with Fragile X that the condition’s alternate medical name literally includes the word.
But not every case of large testicles points to a genetic condition. Sometimes what feels or looks like a bigger testicle is actually swelling from fluid buildup (called a hydrocele), dilated veins in the scrotum (varicocele), or inflammation from an infection. A hydrocele, for instance, collects fluid in the thin sac surrounding the testicle and can make one side of the scrotum noticeably larger without the testicle itself being abnormal. These conditions range from harmless to something that needs treatment, so any sudden change in size or shape is worth getting checked.
Does Bigger Mean More Testosterone?
There is a real, measurable relationship between testicular size and hormone production, but it’s more modest than most people assume. In the study of young men mentioned above, larger testicular volume correlated positively with testosterone levels and with sperm count and motility. That makes biological sense: the testicles are where both sperm and testosterone are produced, so more tissue generally means more output.
That said, the correlation isn’t strong enough to predict an individual’s testosterone level from testicle size alone. Plenty of men with average-sized testicles have perfectly healthy testosterone levels, and a man with larger testicles isn’t guaranteed to have higher levels. Hormone production depends on signals from the brain, overall health, body fat percentage, sleep, and many other factors. Size is one piece of the picture, not the whole thing.
How Size Changes With Age
Testicles reach their full size by the end of puberty, typically in the late teens, and remain relatively stable through early and middle adulthood. After that, they gradually shrink, a process called testicular atrophy. This happens slowly enough that most men don’t notice it. Alongside the size decrease, you may also experience reduced muscle mass and a gradual decline in sex drive, both related to the natural drop in testosterone that comes with aging.
On the other end of the spectrum, testicles that measure 4 mL or less after puberty (about the size of a grape) can signal Klinefelter syndrome, a chromosomal condition that affects roughly 1 in 600 men. So while most people searching this topic are curious about the upper end of the range, unusually small testicles are actually the more clinically significant finding.
How to Check Your Own
You can get a general sense of size and health with a simple self-exam. The best time is after a warm shower, when the scrotal skin is relaxed. Using both hands, place your index and middle fingers under one testicle and your thumbs on top, then gently roll it between your fingers. You’re feeling for hard lumps, smooth rounded bumps, or any change in shape or firmness compared to what you’re used to.
You’ll likely notice a soft, rope-like cord along the back of each testicle. That’s the epididymis, a normal structure that stores and transports sperm. Bumps on the skin of the scrotum itself are usually ingrown hairs or minor skin irritation, not a cause for concern. What you’re watching for is anything new or different on the testicle itself: a hard spot, a sudden increase in size on one side, or a feeling of heaviness that wasn’t there before.