Prostate Volume Calculator
Estimate prostate volume from ultrasound (TRUS) or MRI dimensions using the clinical ellipsoid formula: V = length × width × height × π/6 (or ×0.52 — your choice, shown transparently). Optionally add a total PSA value for PSA density, plus an educational size interpretation and a step-by-step breakdown.
Enter dimensions
Result
— mL (cm³)
Estimated gland weight—
Factor used—
PSA density—
Formula stepssee below
Educational — not medical advice. The category above is a population-level reference band for learning purposes, not a diagnosis. Prostate volume is one data point among many; discuss any result with a qualified clinician.
How the formula works
The prostate is modeled as an ellipsoid — a stretched sphere. An ellipsoid's exact volume is V = π/6 × L × W × H. Ultrasound machines and radiology textbooks commonly round the constant to 0.52 (about 0.7% lower), so both variants are in clinical use and this calculator lets you pick. Some calculator apps label the 0.52 variant the “Cheng formula” — it is the same ellipsoid equation.
Worked example (a typical training case): 4.5 cm × 4.0 cm × 3.5 cm with the 0.52 factor:
4.5 × 4.0 × 3.5 = 63.0 → 63.0 × 0.52 = 32.8 mL. With π/6 the same dimensions give 33.0 mL.
1 mL = 1 cm³ = 1 cc · estimated weight ≈ volume in grams (tissue ≈ 1 g/mL)
Size reference bands (educational)
| Volume | Reference band |
|---|---|
| < 20 mL | Small — typically reported for younger men |
| 20 – 30 mL | Normal — average range for men over 50 |
| 30 – 40 mL | Mildly enlarged |
| 40 – 60 mL | Moderately enlarged |
| > 60 mL | Severely enlarged |
Bands are educational population-level references, not diagnostic thresholds. A volume above ~30 mL is often called prostatomegaly (enlarged prostate), commonly related to age-related benign growth (BPH) — but size alone determines neither symptoms nor risk.
Frequently asked questions
What is the formula for prostate volume?
Prostate volume is estimated with the ellipsoid formula: Volume = length × width × height × π/6, where the three dimensions (in cm) are measured from ultrasound or MRI. The constant π/6 ≈ 0.5236; many ultrasound machines and textbooks round it to 0.52. The result is in milliliters (mL), which equals cubic centimeters (cm³).
Why are there two factors — π/6 (0.5236) and 0.52?
π/6 is the exact geometric constant of an ellipsoid (V = π/6 × L × W × H). The value 0.52 is the same constant rounded for clinical convenience and is the factor used in most ultrasound machines and radiology literature. The difference between the two is about 0.7%, which is negligible compared to measurement variability. This calculator lets you choose either factor transparently.
Which three measurements do I enter?
Enter the three largest diameters from the imaging report: width (transverse, side to side), height (anteroposterior, front to back) — both usually taken from the axial/transverse ultrasound image — and length (craniocaudal, top to bottom), taken from the mid-sagittal image. If the report lists the dimensions in a different order, the multiplication is commutative, so the volume is the same.
Where do I get these measurements?
They come from your radiology or urology report — transrectal or abdominal ultrasound (TRUS) or prostate MRI. Look for a line like 'prostate measures 4.2 × 3.8 × 3.5 cm'. The calculator cannot measure anything itself; it only computes the volume from numbers a clinician recorded.
Can I enter the dimensions in millimeters?
Yes. Select mm as the input unit and the calculator converts each dimension to centimeters before applying the formula (divide by 10). For example, 45 mm × 40 mm × 35 mm gives the same volume as 4.5 cm × 4.0 cm × 3.5 cm.
What is a normal prostate volume?
Educational reference ranges commonly reported in urology literature: under 20 mL is small (typical for younger men), 20–30 mL is the average range for men over 50, 30–40 mL is mildly enlarged, 40–60 mL moderately enlarged, and over 60 mL severely enlarged. These are population-level reference bands, not diagnostic thresholds — interpretation requires a clinician.
What does an enlarged prostate volume mean?
A volume above roughly 30 mL is often described as prostatomegaly (an enlarged prostate), most commonly related to benign prostatic hyperplasia (BPH), a non-cancerous growth with age. However, prostate size does not determine symptoms or cancer risk on its own, and many men with large volumes have no symptoms. Any concern about the number should be discussed with a urologist.
What is PSA density and how is it calculated?
PSA density (PSAD) = total PSA in ng/mL divided by prostate volume in mL, giving ng/mL per cm³. A threshold of 0.15 ng/mL/cm³ is commonly cited in urology literature as a low-risk context value (for example in active-surveillance criteria). It adjusts the PSA level for gland size: the same PSA value is interpreted differently in a 25 mL prostate versus an 80 mL one.
How accurate is the ellipsoid formula?
The ellipsoid method is the de facto standard in clinical practice and correlates well with actual gland volume (reported correlation coefficients of 0.87–0.93 against surgical specimens in published studies). Because the real prostate is not a perfect ellipsoid, individual estimates can vary, and studies note it tends to slightly underestimate true volume. Planimetry (3D contouring) is more accurate but slower, and is used for treatment planning such as brachytherapy.
Can I use this calculator's result to make medical decisions?
No. This is an educational calculator, not a medical device and not medical advice. Prostate volume is only one data point among many (PSA trend, symptoms, exam findings, MRI). Decisions about evaluation or treatment must involve a qualified clinician.
Sources & method notes
- Ellipsoid method as the de facto standard, V = transverse × AP × length × 0.52 — published in Clinical value of prostate segmentation and volume determination on MRI in BPH (PMC4463345).
- “Prostate volume = length × width × height × π/6; the factor π/6 is about 0.52” — urology-textbook.com, TRUS of the Prostate.
- H × W × L × 0.523 ellipsoid on TRUS — Radiation Oncology (Springer), “Variability in MRI vs. ultrasound measures of prostate volume”.
- Volume = height × width × length × 0.523; specimen weight compared at ~1 g/mL — Radiologia Brasileira (SciELO).
- Worked example 4.5 × 4.0 × 3.5 × 0.52 = 32.8 mL — Dr Sam's Imaging Library, “How To Calculate The Prostate Volume On Ultrasound”.
Scope note. This calculator covers the prostate gland (male pelvic organ). For the bladder, see our bladder volume calculator — different organ, different clinical meaning.
Educational — not medical advice. This tool is for learning purposes only. It is not a medical device, does not diagnose any condition, and must not replace the judgment of a qualified clinician. If you have concerns about your health, consult a doctor.
Free tool by NRTechStudio