The short answer
A normal adult prostate is about 20 to 25 mL, roughly the size of a walnut. It grows slowly from around age 40, by about 1.6% a year on average, and a prostate over about 30 mL is usually described as enlarged. But size alone doesn't tell you much. Many men with a large prostate have few symptoms, and some with a modest one have many. Doctors treat your symptoms, not the number.
This article is for general education and is not medical advice. If you have urinary symptoms, see your doctor for a proper assessment.
Average prostate size by age
The figures below come from population studies of men in their 40s to 70s. They are averages, so they include men with and without BPH. Prostate tissue weighs about the same as water, so 1 gram is roughly 1 mL.
| Age | Average prostate size | What it compares to |
|---|---|---|
| 20s–30s | About 20 mL | A walnut |
| 40–49 | About 28 mL | A large walnut |
| 50–59 | About 31 mL | A small apricot |
| 60–70 | About 35 mL | Just under a golf ball (about 40 mL) |
| 75 and over | About 46 mL | A little larger than a golf ball |
Individual men vary widely around these averages. Some enlarged prostates reach 100 mL or more, about two-thirds the volume of a tennis ball.
Why the prostate keeps growing
The prostate grows quickly during puberty, then stays fairly stable until around 40. After that, a second, slower growth phase begins in most men, driven mainly by dihydrotestosterone (DHT). In a five-year study of 631 men in Olmsted County, Minnesota, prostate volume grew by about 1.6% a year on average, and faster in men whose prostates were already larger.
The growth happens in the part of the gland that wraps around the urethra. That's why even modest growth can squeeze the urine channel and cause the symptoms described in our guide to the signs of an enlarged prostate.
How doctors measure prostate size
- Digital rectal exam (DRE). Quick and done in the office. It gives a rough estimate and tends to underestimate larger prostates.
- Transrectal ultrasound (TRUS). An ultrasound probe measures the gland's length, width and height. The volume is estimated with a simple formula: length × width × height × 0.52.
- Abdominal ultrasound. Less precise but needs no internal probe, and is often used to check how well the bladder empties.
- MRI. The most accurate, usually done when prostate cancer is being investigated rather than just to measure size.
Why size matters, and why it often doesn't
Size and symptoms don't track closely. Population studies find only a modest link between prostate volume and how bothersome urinary symptoms are. A man with a 60 mL prostate may urinate normally, while a man with a 30 mL prostate whose growth presses on the urethra may struggle. That's why doctors rely on a symptom score. You can work out yours with our free IPSS calculator.
Size does matter in three practical ways:
- Choosing medicine. 5-alpha reductase inhibitors such as finasteride shrink the prostate, but they mainly help men whose prostate is larger than about 30 mL. Our guide to BPH medication side effects compares the options.
- Reading a PSA test. A larger prostate makes more PSA. Doctors sometimes divide your PSA by your prostate volume (PSA density) to judge whether a raised PSA is more likely from BPH or something that needs a closer look. See our guide to PSA results.
- Choosing a procedure. If surgery is ever needed, prostate size helps decide which procedure suits best. The American Urological Association's 2026 guideline matches several newer procedures to specific size ranges.
Does a large prostate mean cancer?
No. Prostate enlargement from BPH is not cancer and does not turn into cancer. In fact, cancer is often found in normal-sized glands. The two conditions can exist together, though, so new urinary symptoms or a rising PSA should always be checked. We explain the differences in BPH vs. prostate cancer.
Can you make your prostate smaller?
Only prescription 5-ARIs have been shown in large trials to shrink the prostate, by about 18–25% over several months. Lifestyle changes and plant extracts can ease symptoms but haven't been shown to reduce size. We go through the evidence in can an enlarged prostate shrink naturally?
For men with mild to moderate urinary symptoms who want a natural option alongside their doctor's advice, Complete Prostate Health (NPN 80087894) is licensed by Health Canada to help relieve urinary symptoms of BPH.
When to see a doctor
See your doctor if urinary symptoms bother your sleep or daily life, or if your IPSS score is 8 or higher. Get help the same day if you can't urinate at all, see blood in your urine, or have a fever with burning when you urinate.
Frequently asked questions
What is a normal prostate size for a 60-year-old?
On average about 30 to 35 mL, though many healthy men are smaller or larger. What matters more is whether you have bothersome symptoms.
Is a 40 mL prostate big?
It's moderately enlarged, about the size of a golf ball. Many men with a 40 mL prostate have few symptoms and need no treatment beyond good bladder habits.
How fast does the prostate grow?
About 1.6% a year on average after age 40, faster in men who already have a larger prostate.
Can a doctor tell prostate size from a rectal exam?
Roughly. A digital rectal exam gives an estimate but tends to underestimate larger glands. An ultrasound is more accurate.
Does prostate size affect PSA?
Yes. A larger prostate produces more PSA, which is why doctors sometimes look at PSA density, the PSA level divided by prostate volume.
References
- Rhodes T, et al. Longitudinal prostate growth rates during 5 years in randomly selected community men 40 to 79 years old. J Urol. 1999;161(4):1174–9. Abstract
- Bosch JL, et al. Establishing normal reference ranges for prostate volume change with age in the population-based Krimpen study. Prostate. 2007;67(16):1816–24. Record
- Prostate weight by age (compiled from Zhang SJ et al., Asian J Androl 2013, and Bosch JL et al., Prostate 2007). BioNumbers, Harvard Medical School. Entry
- Roehrborn CG, et al. Correlation between prostate size estimated by digital rectal examination and measured by transrectal ultrasound. Urology. 1997. Record
- American Urological Association. Management of lower urinary tract symptoms attributed to BPH: AUA Guideline (2026). AUA announcement
