Prostate volume calculator
Enter three dimensions from MRI, CT or ultrasound to get ellipsoid and bullet volume. Add a PSA for PSA density, then copy the summary.
For educational purposes only. This is not medical advice and does not replace clinical judgment. Check every result against the source guideline.
Longitudinal, maximum on the mid-sagittal image.
Transverse, maximum on the axial image.
Anteroposterior, maximum on the mid-sagittal image.
Enter all three dimensions to see the volume.
The calculator runs in your browser, and the numbers you enter are never sent anywhere.
The formulas
- Ellipsoid volume
- length x width x height x pi / 6 (about 0.52)
- Bullet volume
- length x width x height x 5 pi / 24 (about 0.65)
- PSA density
- PSA (ng/mL) / volume (mL)
Common questions
- How do you calculate prostate volume?
- Multiply length, width and height in centimeters by pi divided by 6, about 0.52. A gland of 4.5 x 4 x 3.8 cm has an ellipsoid volume of 35.8 mL. One cubic centimeter equals one milliliter, so cc and mL are the same number.
- What is the bullet formula?
- It treats the gland as a cylinder with a half ellipsoid on top: length x width x height x 5 pi / 24, about 0.65. MacMahon and colleagues proposed it in Radiology in 2009 from transrectal ultrasound in men presenting for brachytherapy, and some references prefer it for glands under 55 mL.
- Should I use the ellipsoid or the bullet formula?
- Most references use the ellipsoid formula, so it is the default here. In the MacMahon transrectal ultrasound study it underestimated planimetric volume by a mean of 17 percent. Whichever you use, name the formula in the report so that follow-up studies compare like with like.
- How do you calculate PSA density?
- Divide the serum PSA in ng/mL by the prostate volume in mL. A PSA of 6 ng/mL in a 40 mL gland gives a PSA density of 0.15 ng/mL/mL. You will also see the unit written as ng/mL/cc or ng/mL².
- What PSA density is considered high?
- 0.15 ng/mL/mL is a commonly used threshold, and guidelines use other ranges too. It is a guide to suspicion, not a rule-out: PSA density is read alongside the MRI findings and the clinical picture.
- Does this work for other organs?
- The ellipsoid formula is also used to estimate bladder volume and ellipsoid lesions, so that figure applies as an estimate. The bullet formula is specific to the prostate, so ignore it. Leave PSA empty and edit the organ name in the copied text.
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