How this calculator works
Use orthogonal imaging dimensions, not radii. The ellipsoid coefficient is pi/6. The original bullet paper specifies pi/4.8; this page retains it rather than the commonly rounded 0.65. A larger modelled volume gives a lower PSA density for the same PSA. Formula estimates do not replace image segmentation or clinical assessment. The result is an estimate for information only and is not medical advice.
Formula
Ellipsoid volume = L × W × H × pi/6. Original bullet volume = L × W × H × pi/4.8. PSA density = PSA in ng/mL / volume in mL. Rearrange the chosen volume equation for a missing dimension.
Worked example
With 4 × 4 × 3 cm, ellipsoid volume is 8pi = 25.1327 mL and bullet volume is 10pi = 31.4159 mL. With PSA 4 ng/mL, densities are 0.159155 and 0.127324 respectively.
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Frequently asked questions
Why does the bullet result differ from a 0.65 formula?
Dunn and colleagues published pi/4.8, about 0.6545. This page uses that original coefficient.
Can I solve a dimension while comparing models?
Choose a single model first, because the two coefficients imply different missing dimensions.
Is volume a cancer test?
No. Imaging measurements and PSA density support an assessment but cannot diagnose cancer on their own.