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Printed on 6/29/2026
For informational purposes only. This is not medical advice.
The prostate volume calculator uses the prolate ellipsoid formula (V = W × H × L × π/6) to estimate gland volume from three perpendicular measurements obtained via transrectal ultrasound or MRI. Volume is used to calculate PSA density, plan surgical approaches, and assess BPH severity. Feed the volume into [PSA Density Calculator](/tools/psa-density) for cancer risk stratification. Assess urinary symptoms with [IPSS Calculator](/tools/ipss) and bladder emptying with [Post-Void Residual](/tools/post-void-residual). For cancer-confirmed patients, stratify risk with [CAPRA Score](/tools/capra-score).
Formula: V = W × H × L × π/6 ≈ W × H × L × 0.523 (cm → mL)
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Measure the prostate in three perpendicular planes: transverse width (widest left-right dimension), anteroposterior height (front-to-back depth), and cephalocaudal length (top-to-bottom dimension). Measurements are typically taken in millimeters from TRUS or MRI imaging.
Divide millimeter measurements by 10 to convert to centimeters, then calculate: V = Width × Height × Length × 0.523. The 0.523 factor is π/6, the correction factor for the prolate ellipsoid shape. Result is in mL (equivalent to cm³).
Feed volume into [PSA Density Calculator](/tools/psa-density) for cancer risk stratification. Volume above 40 mL supports 5-ARI therapy; above 80 mL may favor HoLEP over TURP. Use alongside [IPSS Calculator](/tools/ipss) and [Post-Void Residual](/tools/post-void-residual) for complete BPH assessment.
Urologists, urologic oncologists
Prostate volume is the denominator in [PSA Density](/tools/psa-density) calculations. Accurate volume measurement directly affects PSAD interpretation for biopsy decisions and active surveillance eligibility. An inaccurate volume produces a proportionally inaccurate PSAD.
Urological surgeons
Volume guides BPH surgical planning: TURP is standard for glands up to approximately 80–100 mL; UroLift is FDA-approved for ≤80 mL without prominent median lobe; HoLEP achieves excellent outcomes for any size and is preferred for very large glands. Document volume before any surgical planning.
Urologists, primary care physicians
5-alpha reductase inhibitors (finasteride, dutasteride) reduce prostate volume by 20–30% over 12–18 months but provide significant benefit primarily for glands over 40 mL. MTOPS trial evidence supports combination therapy for large-volume BPH. Volume-guided prescribing improves outcomes.
Urologic oncologists
Serial prostate volume measurements track gland size trends during active surveillance for low-risk prostate cancer. A rising volume increases PSA from benign tissue — this context is critical for interpreting PSA kinetics. Stable volume with rising PSA is more concerning than volume-proportional PSA rise.
Radiologists, sonographers
The ellipsoid formula is the standard method for prostate volume reporting on TRUS and MRI. Consistent documentation of all three measurements alongside the calculated volume enables accurate serial comparison and PSAD calculation by referring urologists.
Most TRUS reports give measurements in millimeters. Divide by 10 to convert to centimeters before entering into the formula (e.g., 45 mm → 4.5 cm). Entering mm values will give a result 1,000× too high. Double-check the units on your imaging report.
For glands over 80 mL or irregular shapes, MRI planimetric volume (summing cross-sectional areas across all axial slices) is significantly more accurate than the ellipsoid formula applied to three-point TRUS measurements. MRI is preferred when surgical planning requires precision.
Different sonographers or different measurements of the same prostate can yield volumes differing by 10–20%. A reported volume of 45 mL might be anywhere from 36–54 mL. Use volume ranges rather than point estimates when it affects clinical thresholds, especially for the 40 mL 5-ARI and 80 mL surgical eligibility cutoffs.
On average, the prostate grows about 1.2% per year in men with BPH who are not receiving 5-ARIs. Finasteride and dutasteride reduce volume by 20–30% over 12–18 months. Using serial volume measurements to confirm treatment response provides objective evidence of 5-ARI efficacy.
A prominent intravesical median lobe — which causes outlet obstruction and limits UroLift eligibility — may not be well-represented by the ellipsoid formula. TRUS or MRI descriptions of median lobe anatomy should be documented separately from the total volume measurement.
The prolate ellipsoid formula for prostate volume was established by Terris and Stamey (1991) using TRUS. The MTOPS trial (McConnell 2003, NEJM) demonstrated that 5-ARI therapy is most effective for prostate volumes exceeding 25 mL. AUA 2022 BPH guidelines specify prostate volume as a key parameter for treatment selection.
Your calculated prostate volume provides an estimate of gland size based on the prolate ellipsoid formula. A volume under 30 mL is generally considered normal for an adult male. A volume of 30 to 59 mL indicates mild enlargement, which is common with age and may or may not be associated with significant urinary symptoms. A volume of 60 to 99 mL represents moderate enlargement that is more likely to cause obstructive symptoms and may influence treatment selection. A volume of 100 mL or greater indicates severe enlargement and typically requires consideration of surgical approaches suited to very large glands.
Prostate volume is a key input for calculating PSA density, which helps differentiate elevated PSA due to benign hyperplasia from that caused by prostate cancer. Larger prostates naturally produce more PSA from benign epithelial tissue, so a man with a 80 mL prostate and a PSA of 6 ng/mL has a very different risk profile than a man with a 25 mL prostate and the same PSA level.
Prostate volume calculation is indicated whenever prostate size is needed for clinical decision-making. Common scenarios include calculating PSA density during prostate cancer workup, planning surgical approach for BPH treatment (TURP is typically suitable for glands up to 80 mL, while HoLEP or open prostatectomy may be preferred for larger glands), and assessing eligibility for minimally invasive procedures such as UroLift (generally limited to glands of 80 mL or less without a prominent median lobe).
Volume measurement is also used in active surveillance protocols for low-risk prostate cancer, where increasing prostate size over time may affect PSA density trends. In radiation oncology, accurate volume assessment helps with treatment planning for brachytherapy seed placement.
The ellipsoid formula assumes the prostate approximates an ellipsoid shape, which is a simplification. Prostates with prominent median lobes, irregular contours, or asymmetric enlargement may not be accurately represented by this formula. In such cases, planimetric volume calculation from MRI (summing cross-sectional areas across all slices) provides a more precise measurement.
Measurement accuracy depends on the imaging modality and operator skill. Transrectal ultrasound measurements have interobserver variability of 10 to 20%, and small errors in any of the three dimensions are magnified by the multiplication in the formula. MRI-based measurements are more reproducible but require dedicated imaging.
Prostate volume alone does not predict symptom severity. Some men with significantly enlarged prostates have minimal urinary symptoms, while others with only mildly enlarged glands experience severe obstruction due to median lobe anatomy or detrusor dysfunction. Volume should always be interpreted alongside symptom assessment (IPSS), flow studies, and post-void residual measurement.
Disclaimer: This tool is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your health.
April 21, 2026 · trust-baseline
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Calculate PSA density (PSAD) to differentiate BPH from prostate cancer. PSAD ≥0.15 ng/mL/mL indicates higher cancer risk and may warrant biopsy even with borderline total PSA levels.
OpenUrologyCalculate the International Prostate Symptom Score (IPSS/AUA-SI) to assess BPH symptom severity. Mild (0–7): watchful waiting. Moderate (8–19): medications. Severe (20–35): surgical evaluation.
OpenUrologyInterpret post-void residual (PVR) volume for urinary retention and BPH evaluation. PVR <50 mL: normal. 50–200 mL: equivocal. >300 mL: significant retention requiring intervention.
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