Normal Prostate Size
The normal prostate gland volume ranges from approximately 20-30 cc (or grams) in healthy adult men, with volume gradually increasing with age from a mean of 24 cc at age 50 to approximately 38 cc by age 80. 1
Age-Related Normal Values
- In community-dwelling healthy men aged 50-80 years, mean prostate volume increases continuously with aging: starting at 24 cc in men aged 50-59 years and reaching 38 cc in men aged 70-80 years 1
- This age-related enlargement is a normal physiological process and does not necessarily indicate pathology 1
Clinical Significance Thresholds
A prostate volume greater than 30 cc is considered clinically significant when evaluating treatment options for benign prostatic hyperplasia (BPH). 2, 3
- Prostates ≤30 grams are considered small and are appropriate for transurethral incision of the prostate (TUIP) 2
- Prostates >30 cc qualify for treatment with 5-alpha reductase inhibitors (5-ARIs), which are only effective in demonstrably enlarged glands 2, 3, 4
- Prostates >60 grams are considered large and may require simple prostatectomy (open, laparoscopic, or robotic-assisted) rather than transurethral approaches 2
Measurement Considerations
Prostate weight in grams correlates extremely closely with volume in cubic centimeters (cc), making weight an excellent surrogate for volume measurement. 5
- Transrectal ultrasound (TRUS) using the prolate ellipsoid formula (height × width × length × π/6) consistently underestimates true prostate volume by approximately 17% 6
- The dimensional method underestimates the craniocaudal diameter by 13%, anteroposterior diameter by 2%, and transverse diameter by 7% 6
- MRI provides slightly more accurate volume measurements (correlation coefficients 0.80-0.96) compared to ultrasound and CT (0.70-0.90) 7
- Step planimetry is more reproducible than the dimensional method, with a mean error of only 1% versus 8% 6
Important Clinical Caveats
- Prostate shape varies considerably even at the same volume, with different combinations of width, height, and length dimensions 8
- Prostates longer than 4 cm in the longitudinal dimension are associated with significantly more severe lower urinary tract symptoms regardless of total volume 8
- PSA levels also increase with age in healthy men (from 1.1 ng/mL at age 50-59 to 2.5 ng/mL at age 70-80), even in prostates <25 cc 1
- A minimum prostate volume of >30 cc or PSA >1.5 ng/mL is necessary for reliable response to 5-ARI therapy 2