Prostate Volume & PSA Density Worked Examples

July 19, 2026

Four worked examples spanning a small gland, a large BPH-enlarged gland, a genuinely borderline PSAD case, and a side-by-side coefficient comparison.

Example 1 — Small Gland, High PSAD (Higher Suspicion Pattern)

Dimensions: 3.0cm × 2.5cm × 2.5cm. PSA: 4.5 ng/mL.

Volume = 0.52 × 3.0 × 2.5 × 2.5 = 0.52 × 18.75 = 9.75 cc
PSAD = 4.5 ÷ 9.75 = 0.46 ng/mL/cc

A PSAD this far above both the 0.15 and 0.20 thresholds, in a notably small gland, is the pattern most associated with higher suspicion — the PSA elevation is much less likely to be explained by BPH alone when there’s so little tissue volume to account for it.

Example 2 — Large BPH Gland, Reassuring PSAD

Dimensions: 6.0cm × 5.0cm × 5.0cm (a large, BPH-enlarged gland). PSA: 6.0 ng/mL.

Volume = 0.52 × 6.0 × 5.0 × 5.0 = 0.52 × 150 = 78 cc
PSAD = 6.0 ÷ 78 = 0.077 ng/mL/cc

Despite a PSA of 6.0 (which on its own might look concerning), the PSAD here sits well below 0.15 — consistent with a PSA elevation that’s well explained by the sheer size of a benign, enlarged gland rather than a separate cancer-driven process.

Example 3 — Genuinely Borderline Case

Dimensions: 4.0cm × 3.5cm × 3.5cm. PSA: 4.2 ng/mL.

Volume = 0.52 × 4.0 × 3.5 × 3.5 = 0.52 × 49 = 25.48 cc
PSAD = 4.2 ÷ 25.48 = 0.165 ng/mL/cc

This lands between the classic 0.15 threshold and the newer 0.20 alternative — exactly the range where PSA density for primary care & urology explains that PSA velocity, free/total PSA ratio, and any PI-RADS finding carry more decision-making weight than the PSAD number by itself.

Example 4 — Coefficient Comparison (0.52 vs. π/6)

Same dimensions as Example 3 (4.0cm × 3.5cm × 3.5cm), calculated with the more precise π/6 (≈0.5236) coefficient instead of the rounded 0.52:

Volume = 0.5236 × 4.0 × 3.5 × 3.5 = 0.5236 × 49 = 25.66 cc
PSAD = 4.2 ÷ 25.66 = 0.164 ng/mL/cc

The two coefficients produce a difference of about 0.18cc in volume and 0.001 in PSAD — small enough to never change a clinical interpretation, which is why both coefficients remain in routine use. See common prostate volume calculation mistakes for other sources of variation that matter more than this coefficient choice.

Running These Yourself

Every result above matches what the prostate volume calculator produces directly from the same three dimensions and PSA value — enter any real report’s figures to reproduce these calculations, or to check a set of numbers not covered here.