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Prostate Volume Calculator — Ellipsoid Method & PSA Density

Calculate prostate volume from length, width, and height using the ellipsoid formula, plus PSA density (PSAD) with the 0.15 and 0.20 thresholds.

Leave blank to see prostate volume only.

Prostate Volume (Ellipsoid Method)
28.66 cc

Volume = 0.52 × Length × Width × Height (cm), the standard clinical rounding of the ellipsoid coefficient π/6 ≈ 0.523. PSA Density (PSAD) = Serum PSA ÷ Prostate Volume. PSAD is one data point among several used in prostate cancer risk assessment — PSA velocity, free/total PSA ratio, MRI findings (PI-RADS score), age, and family history all factor into an actual clinical decision. This tool is for education and reference only and does not replace evaluation by a urologist.
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Reference Values

Last verified:
Category Range What It Means Status
Ellipsoid Formula Coefficient 0.52 (clinical rounding of π/6 ≈ 0.523) Standard coefficient used in the ellipsoid (prolate spheroid) method for TRUS and MRI prostate volume estimation. Multiplied by length × width × height (all in cm) to yield volume in cc (mL). 0.52 is the conventional clinical rounding; 0.523 is the mathematically exact π/6 coefficient. Good
Typical Adult Gland Volume ~20–30 cc (25 cc average) Approximate normal range for a healthy adult prostate. Volume tends to increase with age due to benign prostatic hyperplasia (BPH) — a large gland alone does not indicate cancer, which is exactly why PSA density adjusts PSA for gland size instead of using raw PSA alone. Good
Normal / Low-Risk PSAD ★ 0.15 ng/mL/cc or below Classic, most widely cited PSA density threshold. Values at or below this level are generally considered less suspicious for clinically significant prostate cancer, though PSAD is only one factor among several used in an actual risk assessment. ★ Best
Elevated PSAD (Classic Threshold) Above 0.15 ng/mL/cc Long-standing threshold associated with increased prostate cancer risk, particularly when total PSA itself falls in the 4–10 ng/mL 'diagnostic gray zone.' Often prompts consideration of further workup such as MRI or biopsy, in combination with other risk factors. Okay
Newer Alternative Threshold 0.20 ng/mL/cc Some more recent analyses — particularly in patients with a negative or equivocal MRI — suggest 0.20 may better distinguish clinically significant cancer and reduce unnecessary biopsies. This is presented as an emerging, alternative consideration alongside the classic 0.15 cutoff, not a replacement for it. Okay

Source: Ellipsoid (prolate spheroid) volume method as used in transrectal ultrasound (TRUS) and MRI prostate volume assessment; PSA density concept and 0.15 ng/mL/cc cutoff originate from Benson et al. (1992, J Urol) and are widely reproduced in urology/radiology reference tools (MDCalc-style clinical calculators, AUA guidance); 0.20 ng/mL/cc alternative threshold drawn from more recent MRI-era PSAD biopsy-decision literature. Aggregated from standard urology/radiology reference sources — always confirm against your urologist's interpretation and institutional protocol.

Worked Examples

Normal-Sized Gland, Normal PSAD

Length
4 cm
Width
3 cm
Height
3 cm
PSA
1.2 ng/mL
Volume = 18.72 cc, PSAD = 0.06 ng/mL/cc

Volume = 0.52 × 4 × 3 × 3 = 0.52 × 36 = 18.72 cc. PSAD = 1.2 ÷ 18.72 = 0.06 ng/mL/cc — well below the 0.15 threshold, consistent with low risk from PSA density alone.

Borderline Case — Classic vs. Newer Threshold

Length
4 cm
Width
3.5 cm
Height
3.5 cm
PSA
5.0 ng/mL
Volume = 25.48 cc, PSAD = 0.196 ng/mL/cc

Volume = 0.52 × 4 × 3.5 × 3.5 = 0.52 × 49 = 25.48 cc. PSAD = 5.0 ÷ 25.48 = 0.196 ng/mL/cc — above the classic 0.15 cutoff (flagged as elevated) but just under the newer 0.20 alternative threshold, illustrating why the two thresholds can disagree on a borderline result.

Enlarged Gland (BPH) — Volume Explains an Elevated PSA

Length
5.5 cm
Width
4.5 cm
Height
4.5 cm
PSA
4.5 ng/mL
Volume = 57.92 cc, PSAD = 0.08 ng/mL/cc

Volume = 0.52 × 5.5 × 4.5 × 4.5 = 0.52 × 111.375 = 57.92 cc. PSAD = 4.5 ÷ 57.92 = 0.08 ng/mL/cc — despite an absolute PSA that could look concerning alone, the larger gland (typical of benign prostatic hyperplasia) brings PSA density back into the normal range.

Small Gland, High PSA — Elevated by Both Thresholds

Length
3 cm
Width
2.5 cm
Height
2.5 cm
PSA
6.0 ng/mL
Volume = 9.75 cc, PSAD = 0.62 ng/mL/cc

Volume = 0.52 × 3 × 2.5 × 2.5 = 0.52 × 18.75 = 9.75 cc. PSAD = 6.0 ÷ 9.75 = 0.62 ng/mL/cc — well above both the classic 0.15 and newer 0.20 thresholds, a pattern that typically warrants further urology workup.

Volume-Only Measurement (No PSA Entered)

Length
4.5 cm
Width
3.5 cm
Height
3.5 cm
PSA
not entered
Volume = 28.67 cc

Volume = 0.52 × 4.5 × 3.5 × 3.5 = 0.52 × 55.125 = 28.67 cc — within the typical adult range (~20–30 cc). PSAD cannot be calculated without a PSA value, so the calculator shows volume only until one is entered.

How to Use This Calculator

  1. 1

    Choose your measurement units

    Select centimeters (the standard imaging report unit) or inches — the calculator converts automatically.

  2. 2

    Enter length, width, and height

    Use the three prostate dimensions from your TRUS or MRI report, measured in the same units.

  3. 3

    Read the calculated volume

    The ellipsoid formula (0.52 × L × W × H) returns volume instantly in cc (mL).

  4. 4

    Optionally enter your PSA to see PSA density

    Enter serum PSA in ng/mL to calculate PSAD and see whether it falls above or below the 0.15 and 0.20 reference thresholds.

What Each Value Means

Prostate Volume (cc (mL))
The estimated size of the prostate gland in cubic centimeters (cc), calculated from length, width, and height measurements using the ellipsoid method. Also referred to interchangeably as mL since 1 cc = 1 mL.
PSA (Prostate-Specific Antigen) (ng/mL)
A protein measured in blood serum that rises with prostate tissue growth, whether from benign enlargement (BPH), inflammation, or cancer. Used as the numerator in the PSA density calculation.
PSA Density (PSAD) (ng/mL/cc)
Serum PSA divided by prostate volume, correcting a raw PSA value for gland size. Higher PSAD relative to volume increases suspicion that a PSA elevation reflects cancer rather than benign enlargement alone.

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Frequently Asked Questions

What is the formula for prostate volume?
Prostate Volume (cc) = 0.52 × Length × Width × Height, with all three dimensions in centimeters from a transrectal ultrasound (TRUS) or MRI. This is the ellipsoid (prolate spheroid) method, the clinical standard for estimating prostate volume from cross-sectional imaging. The 0.52 coefficient is a rounded clinical approximation of the true ellipsoid coefficient, π/6 ≈ 0.523 — both are used in practice, and the difference between them is negligible for clinical purposes.
What does PSA density (PSAD) mean and what does the 0.15 threshold indicate?
PSA density is serum PSA divided by prostate volume (PSAD = PSA ÷ Volume), which adjusts a PSA reading for gland size — a useful correction since benign prostatic hyperplasia (BPH) alone can raise PSA without any cancer present. A PSAD above 0.15 ng/mL/cc is the classic, most-cited threshold suggesting the PSA elevation is less likely to be explained by gland size alone, prompting consideration of further workup such as MRI or biopsy. It is a risk signal, not a diagnosis — PSAD alone does not confirm or rule out cancer, and the threshold works best combined with other factors like PSA velocity, free/total PSA ratio, and MRI findings.
Why do some sources use 0.20 instead of 0.15 for PSAD?
0.15 is the long-standing, most widely cited PSAD cutoff, dating back to early validation studies. More recent research — particularly in patients who have already had a negative or equivocal MRI — has suggested that a higher threshold around 0.20 may better distinguish clinically significant cancer from indolent or benign findings, reducing unnecessary biopsies in that specific population. This calculator shows 0.20 as an emerging alternative consideration alongside the classic 0.15 default, not as a replacement for it — your urologist will weigh which is more relevant to your specific case and imaging history.
Does a normal PSAD rule out prostate cancer?
No. A PSAD at or below 0.15 lowers the statistical likelihood that an elevated PSA is cancer-driven, but it does not rule cancer out on its own, and a normal PSAD in the presence of other red flags (abnormal digital rectal exam, suspicious MRI, family history, rising PSA velocity) should not be treated as reassuring by itself. PSAD is one input among several a urologist uses when deciding whether to recommend an MRI, biopsy, or continued monitoring.
How accurate is the ellipsoid formula compared to true prostate volume?
The ellipsoid formula is a well-validated approximation, but it assumes the prostate is a symmetric ellipsoid shape, which real glands only approximate — asymmetric or irregularly shaped glands (common with significant BPH nodules) introduce more error. Studies comparing ellipsoid-estimated volume to actual surgical specimen or planimetric volume generally show good but imperfect correlation, with some tendency to underestimate larger, more irregular glands. It remains the standard method in routine clinical practice because it only requires three simple measurements already captured on standard ultrasound or MRI.