Normal Adult Prostate Size
The normal adult prostate gland weighs approximately 20 grams (±6 grams) in men aged 21-30 years and remains essentially constant at this size throughout life unless benign prostatic hyperplasia (BPH) develops. 1
Baseline Normal Prostate Measurements
Weight/Volume: The normal prostate proper weighs approximately 11 grams (range 7-16 grams) in adult men when carefully dissected from surrounding non-prostatic tissue. 2
Volume equivalent: Using the standard conversion where 1 gram ≈ 1 cc, the normal prostate volume is approximately 20 cc (±6 cc) in young adult men aged 21-30 years. 1
Age stability: This baseline size remains essentially unchanged with aging in the absence of BPH development. 1
Clinical Significance Thresholds
While the above represents the "normal" prostate, clinical decision-making uses different volume thresholds:
>30 cc (or mL): Considered clinically significant enlargement that qualifies patients for 5-alpha reductase inhibitor therapy and warrants intervention for BPH. 3, 4
>60 grams: Classified as large prostates requiring consideration of simple prostatectomy rather than standard transurethral procedures. 3, 4
Age-Related Changes and BPH Prevalence
Baseline maintenance: In men without BPH, prostate weight remains constant at approximately 20 grams regardless of age. 1
BPH development: When BPH develops, the average prostate weight increases to 33 grams (±16 grams). 1
Prevalence by age: Only 8% of men in their 40s have pathological BPH, but this increases to 50% by ages 51-60 years, and reaches 80% by age 80. 1, 5
Community data: In healthy German men aged 50-80 years without LUTS/BPH, mean prostate volume increased from 24 cc at age 50 to 38 cc at age 80. 6
Important Clinical Caveats
Measurement variability: The commonly used ellipsoid formula with transrectal ultrasound consistently underestimates true prostate volume by approximately 17%, primarily because it underestimates the craniocaudal diameter by 13%. 7
PSA correlation: A PSA >1.5 ng/mL or prostate volume >30 cc is necessary for reliable therapeutic response to 5-alpha reductase inhibitors. 3, 4
Racial differences: Normal prostate volume and PSA reference ranges vary by ethnicity; failure to account for these differences may lead to misinterpretation of results. 4, 5