Prostate Volume Calculator (ellipsoid formula from ultrasound or MRI)

Understanding the prostate volume calculator — concept and principle

This calculator estimates prostate volume from three measurements taken on ultrasound or MRI, using the ellipsoid formula. Urologists and radiologists use the volume to assess enlargement, plan treatment for benign prostatic hyperplasia and calculate PSA density.

Ellipsoid formula: with the default inputs the result is 42.2 mL (over 30 mL → enlarged).

How it is calculated

Volume (mL) = length × width × height (cm) × π ÷ 6

Approximate weight (g) = volume × 1.05

Length is craniocaudal (base to apex on the sagittal view).
Width is the largest transverse diameter.
Height is anteroposterior on the sagittal view.
π ÷ 6 ≈ 0.524.

The principle

The prostate is roughly the shape of an ellipsoid. The volume of an ellipsoid with diameters a, b and c is π ÷ 6 × a × b × c, which is about half of the box that contains it. Prostate tissue has a density close to 1.05 g/mL, so the volume in millilitres is close to the weight in grams. Because three diameters are multiplied, small measurement errors add up.

Worked example

Default inputs: length 4.8 cm, width 4.2 cm, height 4.0 cm.

4.8 × 4.2 × 4.0 = 80.64.
Volume = 80.64 × 0.5236 = 42.2 mL → Over 30 mL – enlarged.
Weight ≈ 42.2 × 1.05 = 44 g.

Each point is the calculator re-run with only “Length – craniocaudal (cm)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Length – craniocaudal (cm)	Prostate volume (mL)
1.2	10.6
2.4	21.1
3.6	31.7
4.8	42.2
6	52.8
7.2	63.3
9.6	84.4

How to read the result

Where does your result fall?

A young adult prostate is about 20–25 mL. Volumes above about 30 mL are usually described as enlarged, and benign enlargement is common with age. Size does not match symptoms well: some men with large glands have few symptoms and vice versa. Volume matters for choosing some treatments and for PSA density.

Common mistakes

Measuring width on the sagittal instead of the transverse view.
Comparing transabdominal measurements, which are less precise, with transrectal or MRI values.
Entering millimetres instead of centimetres.

Keep in mind: This is not a diagnosis. Urinary symptoms and prostate size should be assessed by a doctor.

Frequently asked questions

What is a normal prostate size?

About 20–25 mL in young adults; it grows with age.

Is a larger prostate more likely to be cancer?

Not by itself. Enlargement is usually benign; PSA density helps put PSA in context of size.

How accurate is the ellipsoid formula?

Reasonably good, especially with MRI; very irregular glands may be better measured by segmentation.

Sources: Turkbey B et al., "Prostate Imaging Reporting and Data System Version 2.1", Eur Urol 2019;76(3):340–351 (ellipsoid volume method)

Checked 9 Nov 2026. Ellipsoid formula V = L × W × H × π/6 as standard for transrectal ultrasound and MRI prostate volumetry (standard value; tissue density about 1.05 g/mL).

Your numbers