# What is my prostate volume?

Calculates prostate volume from three ultrasound or MRI measurements with the ellipsoid formula (π/6 × length × width × height), and the PSA density when a PSA value is given.

- Page: https://www.acalculator.org/health/prostate-volume-calculator
- JSON spec: https://www.acalculator.org/health/prostate-volume-calculator.json
- Version: 6fdb3b868f44

## Default answer

Example with the default inputs (Length 4.5 cm, Width 3.5 cm, Height 4 cm): The prostate volume is 33 mL.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| l | Length | The longest dimension of the gland, head to foot (craniocaudal). |
| w | Width | The widest side-to-side dimension (transverse). |
| h | Height | The front-to-back dimension (anteroposterior). |
| psa | PSA (ng/mL) | Optional: the serum prostate-specific antigen, in ng/mL, for the PSA density. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| volume | Prostate volume | The ellipsoid volume in mL (cubic centimeters), to 1 decimal. |
| psad | PSA density (ng/mL per mL) | PSA divided by the prostate volume, to 3 decimals. Shown when a PSA is given. |

## Method

Volume (mL) = π/6 × length × width × height, in cm. PSA density = PSA (ng/mL) ÷ volume (mL).

## Assumptions

- Measurements in centimeters (millimeters are divided by 10); 1 cm³ = 1 mL.
- The volume is rounded to 1 decimal and the PSA density to 3 decimals, halves up; the density uses the unrounded volume.
- The ellipsoid formula is an estimate. It is closest for glands under about 80 mL (Terris and Stamey 1991).

## Worked examples

1. l = 0.045, w = 0.035, h = 0.04, psa = 5 gives volume = 33, psad = 0.152. Source: Π/6 × 4.5 × 3.5 × 4.0 = 32.987 mL (Terris and Stamey 1991, ellipsoid); 5 ÷ 32.987 = 0.1516 (Benson 1992).
2. l = 0.05, w = 0.04, h = 0.045, psa = 3.2 gives volume = 47.1, psad = 0.068.
3. l = 0.06, w = 0.055, h = 0.05 gives volume = 86.4.
4. l = 0.03, w = 0.025, h = 0.028, psa = 1.1 gives volume = 11, psad = 0.1.

## FAQ

### How is prostate volume calculated?

With the ellipsoid (prolate spheroid) formula: volume = π/6 × length × width × height. π/6 is about 0.52, so the formula is often written as length × width × height × 0.52. With the measurements in centimeters, the result is in milliliters (1 cm³ = 1 mL).

### What is a normal prostate volume?

A young adult prostate is about 20 to 25 mL. It often grows with age (benign prostatic hyperplasia). Your radiologist or urologist reads the size in the context of your age and symptoms.

### What is PSA density?

PSA density (PSAD) is the PSA level in ng/mL divided by the prostate volume in mL. Benson and others (1992) proposed it because a large benign gland makes more PSA, so the same PSA means less in a large gland than in a small one.

### How accurate is the ellipsoid formula?

Terris and Stamey (1991) compared ultrasound volume methods with the weight of the removed gland. The ellipsoid volume correlated well (r = 0.90). All ultrasound estimates depend on how the gland is measured.

## Sources

- Terris MK, Stamey TA. Determination of prostate volume by transrectal ultrasound. J Urol. 1991;145(5):984-987. https://doi.org/10.1016/S0022-5347(17)38508-7
- Benson MC, et al. Prostate specific antigen density: a means of distinguishing benign prostatic hypertrophy and prostate cancer. J Urol. 1992;147(3 Pt 2):815-816. https://doi.org/10.1016/S0022-5347(17)37393-7