One Testicle Is Bigger Than the Other — When Is It Normal and When Should You Get It Checked?
It is very common to notice that your testicles are not perfectly identical. One may sit lower, look slightly larger or feel a little different from the other. In many men, this is simply normal anatomy.
However, a new change in the size, shape or firmness of one testicle should not automatically be assumed to be normal. Fluid around the testicle, a cyst, enlarged veins, inflammation and other scrotal conditions can all make one side appear larger. Less commonly, enlargement or a new lump can be caused by a testicular tumour.[1-4]
The most useful question is often not “Are my testicles exactly the same size?” but rather:
“Has something changed from what is normal for me?”
Is it normal for one testicle to be bigger than the other?
Yes. A small amount of natural asymmetry is common.
Studies of healthy adult men have demonstrated measurable differences between the two testes. One study of normal testes found that the right testis was, on average, slightly larger than the left.[1] Research using ultrasound in healthy fertile men has also shown a normal range of testicular sizes rather than one single “correct” measurement.[2]
It is also common for one testicle—often the left—to hang slightly lower.
This means that minor, long-standing asymmetry without a lump, pain or recent change is usually not concerning by itself.[1,2]
What deserves more attention is a difference that has appeared recently, is becoming more noticeable, or is associated with a hard area, lump, heaviness or discomfort.
Sometimes the testicle itself is not actually bigger
This is an important point.
When someone feels that one testicle is larger, the enlargement may actually be coming from structures around the testicle rather than the testicle itself.
Scrotal ultrasound is particularly useful because it can distinguish an abnormality arising within the testis from fluid, cysts, veins and other conditions surrounding it.[3,4]
You can read more about these conditions in the Scrotal & Testicular Conditions section.
What can make one side of the scrotum look or feel bigger?
Normal anatomical difference
If the difference has been present for as long as you can remember, both testes feel smooth and similar in consistency, and there has been no recent change, the asymmetry may simply reflect normal anatomy.[1,2]
Hydrocele
A hydrocele is a collection of fluid around the testicle. It can cause one side of the scrotum to gradually become larger, heavier or more uncomfortable.
The testicle itself may still be normal size—the fluid surrounding it is what creates the enlargement.
Not every hydrocele requires surgery. Treatment depends on its size, symptoms, diagnostic certainty and individual circumstances.
Read more about hydrocele assessment and treatment or the article Hydrocele: When Does It Need Surgery?.
Epididymal cyst or spermatocele
The epididymis is a structure that sits behind and above the testicle. Benign fluid-filled cysts can develop in this area.
A larger epididymal cyst or spermatocele can make one side feel fuller or larger even though the testicular tissue itself is normal.[3]
More information is available on the Epididymal Cyst & Spermatocele page.
Varicocele
A varicocele is enlargement of the veins around the testicle. It occurs more commonly on the left side and can cause fullness, dragging discomfort or a collection of prominent veins above the testicle.
Varicoceles are also relevant in some men being investigated for male infertility, although finding a varicocele does not automatically mean that treatment is required.[2,3]
Infection or inflammation
Inflammation of the epididymis or testicle can cause swelling and tenderness. This may develop alongside pain, urinary symptoms or fever, although symptoms vary.
A suddenly swollen or painful testicle should not simply be assumed to be an infection because several conditions can produce overlapping symptoms.[3]
Inguinal hernia
Part of the abdominal contents can sometimes move down through the groin into the scrotum. This may cause one side to enlarge, particularly while standing, coughing or straining.
Clinical examination and, when necessary, imaging can help distinguish a hernia from a problem arising within the scrotum.[4]
Testicular mass
A testicular tumour can sometimes present as painless enlargement, a new lump, increased firmness or a change in the shape or consistency of one testicle.[5,6]
This does not mean that a larger testicle is likely to be cancer. Many causes of scrotal enlargement are benign.
However, current European and American urological guidelines recommend appropriate assessment when a suspicious testicular mass is identified, with scrotal ultrasound forming a key part of the initial investigation.[5,6]
Does a bigger testicle mean testicular cancer?
Usually, no.
Size difference alone cannot diagnose testicular cancer.
The features that are more important include a new lump within the testicle, focal hardness, progressive enlargement or a persistent change in the way the testicle feels.
Testicular cancer commonly presents without significant pain, so a painless change should not automatically be ignored.[5,6]
If you are specifically worried about a lump or hard area, you may also find these articles useful: My Testicle Feels Hard — Should I Be Worried? and I Found a Lump on My Testicle — Is It a Cyst or Testicular Cancer?.
When should I arrange an assessment?
A long-standing small difference between otherwise normal-feeling testes is generally different from a new or progressive change.
It is reasonable to arrange medical assessment if one testicle has recently become larger, if the difference appears to be increasing, if you can feel a new lump or firm area, if the testicle feels substantially different from the opposite side, or if there is persistent swelling, heaviness or discomfort.
You do not need to diagnose the cause yourself before seeking assessment.
When is testicular swelling an emergency?
Sudden severe testicular pain or rapidly developing swelling requires urgent medical assessment.
One important cause is testicular torsion, where twisting of the spermatic cord interrupts the blood supply to the testicle. This is a time-sensitive surgical emergency. Australian surgical guidance recommends emergency assessment when torsion is suspected.[9]
Do not wait for a routine outpatient appointment or travel to Brisbane for assessment if you develop sudden severe testicular pain, particularly when associated with nausea, vomiting or a suddenly high-riding or unusually positioned testicle.
What test is usually performed?
If examination cannot confidently explain a new difference in testicular size, scrotal ultrasound with Doppler is usually the most useful imaging test.
Ultrasound can compare both testes and determine their volume, identify fluid around a testicle, detect cysts or enlarged veins, and show whether a lump arises within or outside the testicle. It can also assess blood flow.[3,4,7]
Current EAU and AUA testicular cancer guidelines recommend ultrasound when a testicular tumour is suspected.[5,6]
If ultrasound identifies a suspicious solid testicular lesion, further assessment may include blood tests for tumour markers such as AFP, beta-hCG and LDH.[5,6]
Importantly, not every abnormality seen on ultrasound is cancer and not every ultrasound finding requires surgery. Small and incidental testicular lesions can sometimes be benign, and the appropriate pathway depends on the imaging appearance, tumour markers and individual circumstances.[5,6,8]
More detailed information about this assessment pathway is available on the Testicular Cancer & Testicular Masses page.
Could testicular size affect fertility?
Testicular size can provide some information about testicular function, but size alone does not determine whether a man is fertile.
Studies in healthy fertile men have shown an association between testicular volume and measures of sperm production.[2] However, fertility depends on many factors, and a semen analysis is much more useful than trying to estimate fertility by testicular size alone.
If a testicular abnormality is being investigated in someone who wishes to have children in the future, fertility considerations can be incorporated into assessment and treatment planning where appropriate.
What happens if one testicle really is enlarged?
The next step depends entirely on the cause.
A normal anatomical difference may require no treatment. A small asymptomatic cyst or hydrocele may simply be observed. Infection requires a different pathway. A varicocele is treated selectively rather than automatically. A suspicious intratesticular mass requires more urgent specialist assessment.[3-6]
The purpose of assessment is therefore to establish the diagnosis before deciding whether any treatment is necessary.
Surgery should not be recommended simply because the two sides look different.
Brisbane, interstate and international patients
Patients in Brisbane and South-East Queensland can arrange assessment through the Request an Appointment page, with consulting locations at Greenslopes and Springwood.
For interstate patients, previous ultrasound images, radiology reports and specialist correspondence can be useful when planning an assessment. Depending on the clinical situation, some investigations may be completed locally before travelling. A physical examination or additional imaging may still be required before treatment decisions can be made.
For international patients, information about pre-travel assessment, medical record review, investigations and follow-up planning is available through the International Patient Information page.
Urgent symptoms should always be assessed locally rather than delaying treatment in order to travel.
Take-home message
A small difference in testicular size can be completely normal.
What matters more is whether something has changed.
If one side has recently become larger, harder or different in shape, or you have found a new lump or persistent swelling, examination and a scrotal ultrasound can often clarify whether the difference is normal or caused by a condition within or around the testicle.
Most causes of scrotal asymmetry are not testicular cancer, but a new persistent change is worth investigating rather than repeatedly checking it at home.
For assessment of a persistent testicular or scrotal change, you can request an appointment.
References
Tsili AC, Ntorkou A, Giannakis D, Sofikitis N, Argyropoulou MI. Normal testes asymmetry evaluated by apparent diffusion coefficient and magnetization transfer ratio. Acta Radiol. 2017;58(7):883-889. doi:10.1177/0284185116674502.
Lotti F, Frizza F, Balercia G, Barbonetti A, Behre HM, Calogero AE, et al. The European Academy of Andrology ultrasound study on healthy, fertile men: scrotal ultrasound reference ranges and associations with clinical, seminal, and biochemical characteristics. Andrology. 2021;9(2):559-576. doi:10.1111/andr.12951.
Kühn AL, Scortegagna E, Nowitzki KM, Kim YH. Ultrasonography of the scrotum in adults. Ultrasonography. 2016;35(3):180-197. doi:10.14366/usg.15075.
Sommers D, Winter T. Ultrasonography evaluation of scrotal masses. Radiol Clin North Am. 2014;52(6):1265-1281. doi:10.1016/j.rcl.2014.07.014.
European Association of Urology. EAU Guidelines on Testicular Cancer. Arnhem: EAU Guidelines Office; 2026.
Stephenson A, Bass EB, Bixler BR, Daneshmand S, Kirkby E, Marianes A, et al. Diagnosis and treatment of early-stage testicular cancer: AUA guideline amendment 2023. J Urol. 2024;211(1):20-25. doi:10.1097/JU.0000000000003694.
Khatri G, Bhosale PR, Robbins JB, Akin EA, Ascher SM, Brook OR, et al. ACR Appropriateness Criteria® newly diagnosed palpable scrotal abnormality. J Am Coll Radiol. 2022;19(5S):S114-S120. doi:10.1016/j.jacr.2022.02.018.
Cheung JLS, Bhaduri M. A sound approach to stay on the ball—a review of scrotal pathologies on ultrasound imaging. Br J Radiol. 2026;99(1181):847-858. doi:10.1093/bjr/tqag063.
Royal Australasian College of Surgeons. Acute scrotal pain and suspected testicular torsion guidelines. Melbourne: RACS; 2022.
Medical disclaimer
This article provides general educational information only and does not replace individual medical assessment, diagnosis or treatment. Testicular and scrotal symptoms can have many causes, and appropriate investigations and treatment depend on your symptoms, examination findings, imaging and individual circumstances. No particular treatment is appropriate for every patient, and outcomes cannot be guaranteed. If you develop sudden or severe testicular pain, rapidly increasing swelling, fever or become acutely unwell, seek urgent medical assessment.
