Healthy testicles are smooth, oval-shaped organs that feel slightly firm but give way when you press gently, somewhat like a hard-boiled egg without the shell. Most adults have two, each roughly the size of a large olive or small plum, and it is completely normal for one to hang a bit lower or sit slightly larger than the other. Beyond that simple description, though, there is a surprising amount of normal variation in how testicles look, feel, and behave throughout the day, across different temperatures, and over a lifetime.
Size, Shape, and Texture
A typical adult testicle measures roughly 4 to 5 centimeters long and about 2.5 centimeters wide, though healthy men can fall outside that range without anything being wrong. The surface should feel smooth and slightly rubbery. If you roll a testicle gently between your thumb and fingers, you should be able to feel a uniform, somewhat elastic texture all the way around. There are no bones or sharp edges. At the back of each testicle, you can usually feel a softer, slightly bumpy ridge. That ridge is the epididymis, a tightly coiled tube where sperm mature and are stored before ejaculation. It is a normal structure, not a lump to worry about, though people sometimes mistake it for one during self-examination.
The scrotum itself, the pouch of skin that holds the testicles, has its own distinct appearance. Scrotal skin is thinner and more wrinkled than skin on most other parts of the body, and it often has a slightly darker pigmentation than the surrounding thigh or groin skin. Fine hair is common, and small, painless bumps on the scrotal skin are usually hair follicles or sebaceous glands. The midline seam running down the center of the scrotum, called the raphe, is a normal developmental remnant. None of these features signal a problem.
Why One Hangs Lower
Almost everyone notices that their testicles are not perfectly symmetrical. One testicle, most often the left, tends to hang slightly lower than the other. This is normal anatomy, not a defect. The slight difference in position is thought to prevent the two testicles from compressing each other when you sit or move. There is also a modest size difference between the two sides in most men, usually small enough that you would not notice it without deliberately comparing them.
The left side tends to be the one that hangs lower because of subtle differences in blood vessel anatomy. The vein draining the left testicle takes a longer path and enters the kidney vein at a steeper angle than the right, which creates slightly different pressure dynamics. This same anatomy is the reason that varicoceles, which are dilated veins in the spermatic cord, show up on the left side in roughly 80 to 90 percent of cases and are found in about 15 percent of healthy men overall.1PubMed Central. Acute left varicocele in an adult A varicocele often feels like a bag of worms above the testicle when you are standing, and it tends to flatten out when you lie down. Most varicoceles are harmless and are discovered incidentally.
How They Move Throughout the Day
Testicles are not stationary. They rise and fall inside the scrotum constantly, pulled by a thin muscle called the cremaster. This movement is not random; it is the body’s temperature-regulation system at work. Sperm production requires a temperature slightly cooler than core body temperature, so the scrotum acts as a kind of biological thermostat. When you are cold, the cremaster contracts, pulling the testicles closer to the body for warmth. When you are warm, the muscle relaxes and the testicles drop farther away from the body to cool down. You can see this happening in real time if you step into a cold shower versus a hot bath.
Research in animal models has confirmed that this reflex is not trivial. When the cremaster reflex was experimentally impaired in rats exposed to cold, their testicles lost weight and developed damage to sperm-producing tissue, while rats at room temperature were unaffected.2PubMed. Experimental study on the regulation of testicular function by the cremaster reflex in rats The takeaway is that the constant movement you notice is doing something genuinely important. If your testicles seem to ride higher during exercise and lower while lounging in warm weather, that is exactly how the system is designed to work.
The cremaster reflex can also be triggered by touch. Stroking the inner thigh often causes the testicle on that side to rise. Doctors sometimes check this reflex during a physical exam to confirm that the nerve pathways to the scrotum are intact. If you have ever noticed your testicles retract during moments of anxiety or a startle, that is the same reflex being activated by the sympathetic nervous system. It is a normal response, not a sign of a problem.
Changes During Arousal
During sexual arousal, testicles do not just sit passively. They undergo noticeable changes in both position and feel. Studies have shown that testicular volume increases during erection and the testicles are drawn upward, closer to the body. At ejaculation, the pattern reverses: volume decreases and consistency becomes firmer.3PubMed. Physiological considerations of the morphologic changes of the testicles during erection and ejaculation: a canine study The swelling during arousal is caused by increased blood flow to the testicular tissue, and the elevation is driven by cremaster contraction pulling the testicles into position for ejaculation. If you have noticed that your testicles feel slightly different during or after sex, this is the explanation, and it is entirely normal.
How Testicles Change with Age
Testicles are not the same size your whole life. They grow rapidly during puberty, peak in volume around age 30, and then hold relatively steady in a plateau that lasts until about age 60. After 60, testicular volume tends to decrease in a measurable way.4PubMed. The effects of aging on testicular volume and glucose metabolism: an investigation with ultrasonography and FDG-PET This decline is gradual and part of normal aging, much like how muscle mass, bone density, and many other tissues change over the decades. A man in his 70s should not be alarmed if his testicles feel smaller than they did in his 30s, as long as the change has been slow and there is no associated pain, hardness, or new lumps.
During puberty, testicle growth is often the first visible sign of sexual development, sometimes appearing before any significant growth of pubic hair or the penis. Parents and adolescents sometimes worry if one testicle seems to develop ahead of the other, but asymmetric growth is common and usually resolves on its own as puberty progresses.
What Underwear and Heat Exposure Actually Do
Because temperature regulation is so central to testicular function, lifestyle factors that affect scrotal temperature have attracted real scientific attention. The findings are fairly intuitive: tight-fitting underwear raises scrotal temperatures compared with loose-fitting underwear or going without.5Human Reproduction. Influence of the type of undertrousers and physical activity on scrotal temperature Prolonged sitting at work also correlates with higher daytime scrotal temperatures, and those higher temperatures in turn correlate with lower semen quality.6PubMed. Influence of genital heat stress on semen quality in humans
That said, the practical effect of switching from briefs to boxers is modest for most men. The temperature differences are real but small, and they matter most for men who are already on the borderline of fertility. For everyday comfort and general health, underwear choice is unlikely to make a dramatic difference. The popular worry about saunas damaging sperm has not been strongly supported by the available evidence either.6PubMed. Influence of genital heat stress on semen quality in humans Hot baths, laptop heat, and heated car seats come up frequently in online discussions, and while chronic, repeated heat exposure can theoretically impair sperm production, occasional exposure is unlikely to cause lasting harm.
Lumps, Bumps, and What Is Usually Harmless
Finding a lump on or near a testicle is alarming, but the majority of scrotal masses turn out to be benign. Some of the most common things you might feel include:
- Epididymal cysts: Small, fluid-filled sacs on the epididymis at the back of the testicle. They feel smooth, round, and separate from the testicle itself. They are usually painless and harmless.
- Varicoceles: Enlarged veins above the testicle, often described as feeling like a bag of worms, most commonly on the left side. They may ache after prolonged standing.
- Hydroceles: A collection of fluid around the testicle that makes the scrotum appear swollen. They typically cause a smooth, even enlargement rather than a discrete lump.
- Spermatoceles: Cysts that form in the epididymis and contain fluid and dead sperm cells. They feel similar to epididymal cysts and are almost always benign.
The key distinction doctors look for is whether a mass is inside the testicle or outside it. Masses inside the testicular tissue are more likely to be serious, including the possibility of testicular cancer, while masses outside the testicle in surrounding structures are overwhelmingly benign. When there is any uncertainty, scrotal ultrasound is the standard next step. High-frequency ultrasound can accurately detect abnormal scrotal contents and separate testicular from extratesticular problems with very high accuracy.7PubMed. Diagnostic capabilities of high-resolution scrotal ultrasonography: prospective evaluation In most cases, combining a physical exam with ultrasound findings is enough to reach a diagnosis without surgery.8PubMed Central. Ultrasonography of the scrotum in adults
Getting Familiar with Your Own Normal
The value of knowing what your testicles normally feel like is not about performing a rigorous monthly self-exam on a strict schedule. It is about having a baseline familiarity so that if something changes, you notice. The concept of “testicular awareness” captures this well: being familiar with your own anatomy, knowing the difference between normal and abnormal, being able to detect a change, and understanding your own risk factors.9International Journal of Men’s Social and Community Health. Testicular Awareness: The What, the Why, and the How
The best time to check is after a warm shower or bath, when the scrotum is relaxed and the testicles are hanging naturally. Roll each testicle gently between your thumb and fingers. You are feeling for the smooth, uniform texture described above. The epididymis at the back is normal. What you want to watch for is a hard, painless lump within the body of the testicle itself, a sudden change in size on one side, a feeling of heaviness or dragging, or any new persistent pain. Testicular cancer, the most common solid tumor in young men between roughly 15 and 35, typically presents as a painless lump, which is why baseline familiarity matters so much. Most lumps are not cancer, but the ones that are tend to be highly treatable when caught early.
When Something Feels Off
A few specific scenarios warrant prompt medical attention rather than a wait-and-see approach. Sudden, severe pain in one testicle, especially if accompanied by swelling and nausea, could indicate testicular torsion, where the spermatic cord twists and cuts off blood supply. Torsion is a surgical emergency with a window of only a few hours before permanent damage occurs. A new, hard, painless lump within the testicle itself should be evaluated with ultrasound even if it does not hurt. Gradual swelling on one side, heaviness that worsens through the day, or a dull ache that does not go away after a few days are also worth getting checked.
On the other hand, mild, fleeting discomfort after sitting in a cramped position, slight soreness after vigorous exercise, or temporary tightness in cold weather are all normal sensations. The testicles have an unusually rich nerve supply, which is why they are so sensitive to impact, but that same sensitivity can produce minor aches that mean nothing. Context matters. Pain that comes on suddenly and is severe is very different from a vague ache that comes and goes with position changes.
What Testicular Prostheses Feel Like
Some men have one or both testicles removed due to cancer, torsion, or other conditions, and testicular prostheses are available to restore a natural appearance and feel. If you are curious about how these compare to the real thing, the data is generally encouraging. In studies of men who received implants, about 96 percent reported satisfaction with the prosthesis overall. The main complaint was that about a quarter of recipients described the implant as “too firm.”10PubMed Central. Testicular prostheses – impact on quality of life and sexual function This makes intuitive sense: a natural testicle has a slight give to it that is difficult to replicate with a silicone implant. Partners sometimes notice the firmness difference, and the implant does not change size or position with temperature the way a natural testicle does. Still, for many men, the cosmetic and psychological benefit of having a normal-looking scrotum outweighs the difference in feel.
Prostheses come in different sizes to match the remaining testicle or approximate a natural size, and they are placed inside the scrotum through a small surgical incision. Over time, scar tissue forms around the implant and it stays in position. The implant does not produce hormones or sperm, so it is purely cosmetic and psychological in function. Men considering a prosthesis after orchiectomy should know that the firmness issue is the most commonly reported drawback, but that overall satisfaction rates are high.
Common Misconceptions Worth Clearing Up
One widespread belief is that testicles should be perfectly identical in size, shape, and position. They almost never are. Slight asymmetry is the rule, not the exception, and it does not affect fertility or sexual function. Another misconception is that a testicle that retracts upward during cold exposure or anxiety has “gone back inside” in a way that is dangerous. In most cases, this is simply an exaggerated cremaster reflex and is benign, though men who experience a testicle that fully retracts into the inguinal canal on a regular basis should mention it to a doctor to rule out a retractile testicle that might need monitoring.
There is also a persistent myth that blue or purplish discoloration of the scrotal skin is a sign of disease. Scrotal skin has a particularly high density of blood vessels close to the surface, and veins can be visible through the thin skin, giving a bluish tint that is entirely normal. Actual concerning color changes would include redness with warmth and swelling, which could suggest infection, or sudden dark discoloration, which could indicate trauma or torsion. The normal, baseline bluish hue of visible veins is not something to worry about.
Finally, many men believe that testicular self-exams need to be done on a specific schedule, like a monthly ritual, to be useful. In reality, the evidence for a rigid self-exam schedule is thin, and most major medical organizations emphasize awareness over protocol. If you handle your testicles regularly enough to notice when something is new, whether that is through deliberate checking or just through normal daily routines, you are doing enough. The goal is not to catch something on exactly the right day but to have enough familiarity with your own anatomy that a real change stands out.