Each testicle is a smooth, egg-shaped organ about the size of a large olive or small walnut in adults, sitting inside the scrotum. They feel firm but slightly springy, similar to a hard-boiled egg without the shell. Most people searching this want to know what’s normal, so here’s a detailed look at healthy testicles, the scrotum that holds them, and the changes you can expect throughout life.
Size and Shape
A fully developed adult testicle measures roughly 4 to 5 centimeters long (about 1.5 to 2 inches) and holds a volume of around 15 to 25 milliliters. That’s comparable in size to a walnut or a small plum. The surface is smooth and oval, with no visible ridges or bumps when viewed through the scrotal skin. If you gently roll a testicle between your fingers, it should feel uniformly firm with a slight give, and the surface should be free of hard lumps or irregular spots.
One testicle is almost always slightly larger than the other. Research confirms that the right testicle tends to be the bigger one in most men, though the difference is usually small enough that you’d only notice it on close comparison.
Why One Hangs Lower
It’s completely normal for one testicle to hang lower than the other. In a study of over 4,300 men from the Kinsey data, about 62% reported that the left testicle hangs lower. Around 21% said the right hung lower, and about 17% noticed no difference at all. This asymmetry likely comes from differences in the muscles and blood vessels on each side of the lower abdomen. The staggered positioning actually helps prevent the testicles from compressing against each other.
What the Scrotum Looks Like
The scrotum is a loose pouch of skin divided into two compartments, one for each testicle. The skin has a distinctive wrinkled, ridged texture. These folds are called rugae, and they allow the scrotum to expand and contract as needed. Scrotal skin is typically darker than the surrounding skin on the thighs and abdomen, regardless of overall skin tone. This darker pigmentation is normal and becomes more pronounced after puberty.
You’ll often notice a visible line running vertically down the center of the scrotum. This is the scrotal raphe, a natural seam that marks where the two halves fused during fetal development. It extends from the underside of the penis, along the scrotum, and back toward the anus. It’s purely cosmetic and has no function after birth.
How Temperature Changes Their Appearance
Testicles visibly change position throughout the day based on temperature and stress levels. In warm conditions, small muscles surrounding the testicles relax, and the scrotum hangs low and loose. The skin appears smoother and the testicles sit farther from the body. In cold temperatures or during moments of stress or physical exertion, two different mechanisms pull the testicles upward. Tiny muscles called cremaster muscles actively contract and draw each testicle closer to the body, while separate muscle fibers in the scrotal wall itself cause the skin to tighten and shrink.
This is why the scrotum can look dramatically different from one hour to the next. A tight, compact scrotum pulled close to the body in cold weather is just as normal as a loose, pendulous one after a hot shower. The whole system exists to keep the testicles at a temperature slightly below core body temperature, which is necessary for sperm production.
Structures You Can Feel
When you examine your testicles, you’ll notice more than just the two oval organs. Along the back and top of each testicle sits the epididymis, a soft, comma-shaped structure. It’s a tightly coiled tube that stores and transports sperm. You can feel it as a slightly softer ridge running along the back of the testicle. It has three sections: a head at the top of the testicle, a body running along the back, and a tail at the bottom that connects to the vas deferens, the tube that carries sperm upward during ejaculation.
Above each testicle, you can also feel the spermatic cord, which runs upward into the groin. This cord contains blood vessels, nerves, and the vas deferens bundled together. It feels like a smooth, flexible rope. Under normal conditions, you shouldn’t be able to see or feel individual veins within the cord. If the veins become enlarged and feel like a “bag of worms” in the scrotum, particularly when standing, that’s a varicocele. These are most common on the left side and are visible in more advanced cases.
How They Change During Puberty
Testicular growth is actually the first sign of puberty in boys, starting before other changes like body hair or voice deepening. Before puberty, each testicle is smaller than 4 milliliters in volume, with a long axis under 2.5 centimeters. That’s roughly the size of a marble.
Growth happens in stages over several years. In early puberty, testicular volume increases to 4 to 8 milliliters and the long axis reaches about 2.5 to 3.3 centimeters. Through mid-puberty, they continue growing to 9 to 12 milliliters, then 15 to 20 milliliters. By the end of puberty, each testicle reaches 20 milliliters or more, with a long axis over 4 centimeters. The scrotum also darkens in color, thins out, and develops more pronounced rugae during this process.
What’s Not Normal
Knowing what healthy testicles look and feel like makes it easier to spot something unusual. A few things worth paying attention to:
- Hard, painless lumps on the surface of the testicle itself (not on the epididymis behind it) are the most important finding to have evaluated. Most turn out to be benign, but a firm lump attached to the testicle is the classic sign that needs medical imaging.
- Sudden swelling or pain on one side, especially if it comes on within hours, can signal torsion (the testicle twisting on its cord and losing blood supply). This is a medical emergency.
- A heavy or dragging sensation with visible enlarged veins, particularly on the left side, suggests a varicocele. These are common and usually harmless but can occasionally affect fertility.
- Fluid buildup that makes one side of the scrotum look swollen and feel like a water balloon is typically a hydrocele. The scrotum may appear larger but the testicle inside is usually normal.
- A significant size change in one testicle, where it noticeably shrinks or grows over weeks to months, is worth getting checked.
Monthly self-exams are easiest after a warm shower, when the scrotum is relaxed and hanging naturally. Gently roll each testicle between your thumb and fingers, feeling for the smooth surface of the testicle and the softer epididymis along the back. Familiarity with your own baseline makes it much simpler to notice when something has changed.