Prostate Volume & PSA Density
Ellipsoid formula · live calculation · color-coded PSA density
Dimensions in
Interpretation
Prostate Volume
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PSA Density
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Threshold 0.15 ng/mL/cc
Volume = Height × Width × Length × 0.52 · PSA Density = PSA ÷ Volume
The prolate ellipsoid formula (× 0.52) is the PI-RADS v2.1 standard, but it
underestimates planimetric gland volume by about 17% on average
(95% CI 14–19%). Because volume is the denominator, that inflates PSA density —
so a value sitting just above a threshold may not be above it in truth.
Simple mode uses the classic 0.15 ng/mL/cc cut-off.
EAU bands mode uses the PSA-density strata
(< 0.10 / 0.10–0.15 / 0.15–0.20 / > 0.20) from the
EAU Prostate Cancer Guidelines — Diagnostic Evaluation,
where the biopsy decision depends on PSA density together with the PI-RADS category.
The 0.15 cut-off is a long-standing convention rather than a reassurance threshold: Nordström et al., Prostate Cancer Prostatic Dis 2018 (5,291 men) found 0.15 detected only 49% of Gleason ≥ 7 cancers versus 77% at 0.10, and favoured the lower cut-offs.
The 17% ellipsoid underestimate is from Matthews et al., Radiology 2009, which found most glands to be bullet- rather than ellipsoid-shaped and put 75% of bullet-formula volumes (× π/4.8 ≈ 0.65) within 10% of planimetry, versus 13% for the ellipsoid. This calculator still computes the ellipsoid volume, because PI-RADS v2.1 and the PSA-density thresholds above are both defined on it — swapping the coefficient would lower every density by about a quarter and invalidate the cut-offs.
The 0.15 cut-off is a long-standing convention rather than a reassurance threshold: Nordström et al., Prostate Cancer Prostatic Dis 2018 (5,291 men) found 0.15 detected only 49% of Gleason ≥ 7 cancers versus 77% at 0.10, and favoured the lower cut-offs.
The 17% ellipsoid underestimate is from Matthews et al., Radiology 2009, which found most glands to be bullet- rather than ellipsoid-shaped and put 75% of bullet-formula volumes (× π/4.8 ≈ 0.65) within 10% of planimetry, versus 13% for the ellipsoid. This calculator still computes the ellipsoid volume, because PI-RADS v2.1 and the PSA-density thresholds above are both defined on it — swapping the coefficient would lower every density by about a quarter and invalidate the cut-offs.