What is the ellipsoid formula for prostate volume?

Volume (mL) = Length × Width × Height × 0.523. The factor 0.523 approximates π/6, the correction that converts a rectangular bounding box to the volume of a prolate ellipsoid — the shape the prostate most closely resembles.

What units should I enter?

All three dimensions should be in centimeters (cm) as reported on your ultrasound or MRI. The resulting volume is in milliliters (mL), which are numerically equal to cubic centimeters (cc or cm³).

What is a normal prostate volume?

A normal adult prostate is typically 20–30 mL. Volumes of 30–50 mL indicate mild enlargement (BPH), 50–80 mL moderate enlargement, and above 80 mL is considered a large gland. Volume generally increases with age.

How does prostate volume affect PSA density?

PSA density (PSAD) = PSA ÷ Volume. A large benign prostate naturally produces more PSA; PSAD corrects for this. A PSAD ≥0.15 ng/mL² raises concern for prostate cancer regardless of the absolute PSA level.

Is the ellipsoid formula accurate?

The prolate ellipsoid formula is the standard clinical method for TRUS volume estimation. It has a reported accuracy within 10–15% of planimetric (step-section) MRI volume. It is accepted in all major urology guidelines (AUA, EAU).

Should I use the length, width, or height as which dimension?

Conventions vary slightly by institution, but the formula is commutative — it does not matter which label you assign to which measurement. Simply enter the three distinct cm values from your report.

Prostate Volume Calculator

Name: Prostate Volume Calculator
Availability: InStock
Author: Nham Vu

Enter the three ultrasound dimensions of the prostate gland to calculate volume via the ellipsoid formula, then optionally input PSA to get PSA density.

Prostate Dimensions

Length (cm)

Width (cm)

Height (cm)

All three values from your TRUS or MRI report in cm.

Optional — PSA Density

Total Serum PSA (ng/mL, optional)

Enter to also calculate PSA density (PSAD).

Formula

V = L × W × H × 0.523

Prolate ellipsoid approximation (π/6 ≈ 0.523)

Result

Enter the three prostate dimensions to see volume.

Prostate Volume

mL (cc)

Measurement	Value
Length
Width
Height
PSA Level

Volume Reference

20 – 30 mL Normal

30 – 50 mL Mildly Enlarged

50 – 80 mL Moderately Enlarged

> 80 mL Large

For educational purposes only. Prostate volume and PSA density are inputs to clinical decisions; consult a qualified urologist for diagnosis and treatment planning.

Summary

Enter the three ultrasound dimensions of the prostate gland to calculate volume via the ellipsoid formula, then optionally input PSA to get PSA density.

How it works

Enter the three prostate dimensions in centimeters (from your TRUS or MRI report): length, width, and height.
The tool multiplies all three dimensions by the ellipsoid correction factor 0.523 to approximate gland volume in mL.
Optionally enter your total serum PSA (ng/mL) — the tool will divide PSA by volume to calculate PSA density.
Review the volume classification (normal, mildly enlarged, moderately enlarged, or large) and PSA density risk band.
Share the results with your urologist for clinical interpretation and treatment decisions.

Use cases

Grading BPH severity before considering medications or surgery.
Calculating PSA density to contextualize a borderline PSA reading.
Planning prostate biopsy core count based on gland size.
Tracking prostate volume change over time with serial ultrasounds.
Patient education: understanding gland size and its relationship to urinary symptoms.

Frequently Asked Questions

Last updated: 2026-07-24 · Reviewed by Nham Vu