Prostate volume calculator

Enter the length, width and height already recorded on an ultrasound or MRI report to estimate prostate volume in milliliters, with the calculation shown step by step.

How the calculation works

Imaging reports estimate prostate volume from three dimensions: length, width and height. The common approach is the prolate ellipsoid formula, length x width x height x pi/6, which is about 0.52 (Wu et al.; Narayanamurthy et al.). This calculator converts millimeters to centimeters, multiplies the three dimensions, then multiplies by 0.52. The answer is in milliliters, the same as cubic centimeters.

Volume in mL = length in cm x width in cm x height in cm x 0.52

For example, 40 mm x 35 mm x 30 mm becomes 4.0 cm x 3.5 cm x 3.0 cm. The product is 42.0 cm³, and 42.0 x 0.52 = 21.8 mL. One mL is often treated as roughly one gram, though the conversion is not exact; one study used a density of 1.05 g/mL (Wu et al.).

How to read the result

Published prostate volumes are averages from particular groups, not personal cutoffs. In a German community sample of 1,763 men ages 50 to 80, mean volume rose from 24 cc at age 50 to 38 cc at age 80, and prostate size had only a minor impact on symptom scores (Berges and Oelke). A 15-year Japanese community study reported mean volume rising from 17.4 mL to 23.9 mL, and grouped baseline volumes as under 20 mL, 20 to 25 mL, and 25 mL or more (Fukuta et al.). That is why 20 to 25 mL is a rough landmark here, not a line between normal and abnormal.

A result under 20 mL is below that landmark; 20 to 25 mL sits within it; 25 to 30 mL is above it but below the 30 mL level one ultrasound study used to group larger glands (Choi et al.). A result of 30 mL or more is at or above that study grouping. Reports may describe a larger gland as enlarged, but the word describes size, not a diagnosis. Some men with larger glands have few urinary symptoms, and some with smaller glands have bothersome ones.

For age-related averages, see normal prostate size and volume by age. For urinary symptoms, enlarged prostate symptoms explains what to note, and the overview of enlarged prostate treatment options covers the general categories.

Limits of the formula

The formula assumes an ellipsoid shape, and many glands are not ellipsoid. In a study of 138 men having brachytherapy, the conventional formula was within 10 percent of a planimetric reference in only 13.3 percent of cases and underestimated volume by 17 percent on average (MacMahon et al.). A smaller study found transrectal ultrasound underestimated volume by 21.4 percent versus physical sections (Acer et al.).

Measurements also vary between observers. In one transrectal ultrasound study, differences were larger for glands of 30 mL or more and between less experienced observers (Choi et al.). MRI and ultrasound can give different estimates; in one comparison with surgical specimens, MRI was slightly more accurate (Paterson et al.), and correlations with anatomic weight were 0.79 for MRI, 0.78 for CT and 0.67 for transrectal ultrasound (Narayanamurthy et al.).

This calculator cannot know your report's method, how the dimensions were drawn, or whether the numbers were rounded. Compare your result with the volume and reference range printed by the imaging center, not with a number from a different scan type. This tool is for numbers already in a report, not for self-measurement. For the home-check question, see how to check for an enlarged prostate at home.

What to bring to a doctor

Bring the imaging report itself, not just the calculated volume. The report should show the dimensions, unit, method and any volume. Bring earlier prostate imaging if you have it for comparison.

Write down what you have noticed: a weak stream, trouble starting, urgency, frequency, nighttime trips, pain, blood, fever, or trouble passing urine. A short note about when symptoms began is more useful than a single number. The guides on waking up at night to pee after 50 and a weak urine stream in men over 50 explain what to note.

Bring your medicine list, and ask whether anything could affect urination. Do not stop or change a medicine on your own. Our guide to what a prostate exam involves explains what a clinician may check. For background on medicine classes, see BPH medicines explained, but keep any change to a conversation with your prescriber. Bring two or three questions about the result.

A note on supplements

For a neutral look at prostate supplement labels and the evidence behind them, see our prostate supplement comparison.

Frequently asked questions

What is the prostate volume formula?

The common formula is length x width x height x 0.52, where 0.52 is approximately pi divided by 6. Imaging studies use this formula with ultrasound or MRI dimensions (Wu et al.; Narayanamurthy et al.).

Is prostate volume in mL the same as grams?

They are close but not identical. For practical purposes, 1 mL is often treated as roughly 1 g; one study used a density of 1.05 g/mL when relating prostate weight to volume (Wu et al.).

What is a normal prostate volume?

No single number defines normal for every man. In a German community sample, mean volume rose from 24 cc at age 50 to 38 cc at age 80 (Berges and Oelke). A 15-year Japanese study grouped baseline volumes as under 20, 20 to 25, and 25 mL or more, with mean volume rising from 17.4 to 23.9 mL (Fukuta et al.). These are averages, not personal cutoffs.

Does a larger prostate always cause symptoms?

No. In the German community study, prostate size had only a minor impact on symptom scores (Berges and Oelke). A clinician looks at the urinary pattern and other findings, not just the volume.

Why does my calculated volume differ from the report?

The report may use a different formula, different rounding, or a different imaging method. The conventional ellipsoid formula underestimated volume by 17 percent on average in one study (MacMahon et al.), and transrectal ultrasound measurements can vary between observers (Choi et al.). Ask the imaging center which method it used.

Can I use this to check my prostate at home?

No. This tool only does arithmetic on numbers already recorded by a clinician or imaging center. It cannot measure your prostate, and a home check cannot replace imaging when a measurement is needed.

References

1. Wu S, Feldman AS, Lin SX, et al. Estimated prostate volume by semiautomatic segmentation of MRI is more accurately correlated with radical prostatectomy specimen weight than the volume calculated by ellipsoid formula. Urol Int. 2024;108(1):35-41.
2. Narayanamurthy V, Mishra K, Mahran A, et al. Inter-imaging accuracy of computed tomography, magnetic resonance imaging, and transrectal ultrasound in measuring prostate volume compared to the anatomic prostatic weight. Turk J Urol. 2020;46(1):50-56.
3. MacMahon PJ, Kennedy AM, Murphy DT, Maher M, McNicholas MM. Modified prostate volume algorithm improves transrectal US volume estimation in men presenting for prostate brachytherapy. Radiology. 2009;250(1):273-280.
4. Acer N, Sofikerim M, Ertekin T, Unur E, Cay M, Ozturk F. Assessment of in vivo calculation with ultrasonography compared to physical sections in vitro: a stereological study of prostate volumes. Anat Sci Int. 2011;86(2):78-85.
5. Choi YJ, Kim JK, Kim HJ, Cho KS. Interobserver variability of transrectal ultrasound for prostate volume measurement according to volume and observer experience. AJR Am J Roentgenol. 2009;192(2):444-449.
6. Paterson NR, Lavallee LT, Nguyen LN, et al. Prostate volume estimations using magnetic resonance imaging and transrectal ultrasound compared to radical prostatectomy specimens. Can Urol Assoc J. 2016;10(7-8):264-268.
7. Berges R, Oelke M. Age-stratified normal values for prostate volume, PSA, maximum urinary flow rate, IPSS, and other LUTS/BPH indicators in the German male community-dwelling population aged 50 years or older. World J Urol. 2011;29(2):171-178.
8. Fukuta F, Masumori N, Mori M, Tsukamoto T. Internal prostatic architecture on transrectal ultrasonography predicts future prostatic growth: natural history of prostatic hyperplasia in a 15-year longitudinal community-based study. Prostate. 2011;71(6):597-603.
9. Mavrotas J, Gandhi A, Kalogianni V, Patel V, Batura D. Acute urinary retention. Br J Hosp Med (Lond). 2022;83(1):1-8.
10. Tu WH, Shortliffe LD. Evaluation of asymptomatic, atraumatic hematuria in children and adults. Nat Rev Urol. 2010;7(4):189-194.
11. Coker TJ, Dierfeldt DM. Acute bacterial prostatitis: diagnosis and management. Am Fam Physician. 2016;93(2):114-120.

This tool is general information and is not medical advice. It does not diagnose a condition. Talk to your doctor about your report and symptoms, especially if you take medication or have a medical condition.