Case 1
- Length (top to bottom)
- 4.5cm
- Width (side to side)
- 4cm
- Height (front to back)
- 3.5cm
33.0mL
Open with these valuesProstate Volume Calculator
33.0mL
Result: 33.0 mLThe gland is modelled as an ellipsoid, so the volume is length × width × height × π/6, the coefficient usually quoted as 0.52. Diameters of 4.5, 4.0 and 3.5 cm give about 33 mL. It is a size estimate from numbers your imaging report already contains, not a finding.
The numbers at a glance
Held fixed: Length (top to bottom) 4.5 cm, Width (side to side) 4.0 cm.
| Height (front to back) (cm) | Result (mL) |
|---|---|
| 1.0 | 9.4 |
| 2.0 | 18.8 |
| 3.0 | 28.3 |
| 3.5Your value | 33.0 |
| 4.0 | 37.7 |
| 5.0 | 47.1 |
| 6.0 | 56.5 |
| 7.0 | 66.0 |
Worked examples
Case 2
- Length (top to bottom)
- 3cm
- Width (side to side)
- 3cm
- Height (front to back)
- 3cm
14.1mL
Open with these valuesCase 3
- Length (top to bottom)
- 6cm
- Width (side to side)
- 5cm
- Height (front to back)
- 4cm
62.8mL
Open with these valuesHow it's calculated
V = π/6 × length × width × height, with π/6 ≈ 0.52
- StepTake the three diameters from a transrectal ultrasound or MRI report, in centimetres.
- StepIf the report gives millimetres, divide each by 10 before entering them.
- ResultRead the volume in millilitres — a millilitre and a cubic centimetre are the same thing.
What this number means
The gland is modelled as a prolate ellipsoid, so its volume follows from three diameters and nothing else: length × width × height × π/6, the coefficient usually quoted as 0.52. The preset diameters of 4.5, 4.0 and 3.5 cm multiply to 63, and 63 × π/6 is 33.0 mL. A millilitre and a cubic centimetre are the same unit, so a report stating cc needs no conversion — but a report stating millimetres does, and 45 × 40 × 35 has to become 4.5, 4.0 and 3.5 before it goes into the fields. The three numbers come from a transrectal ultrasound or prostate MRI, usually labelled longitudinal, transverse and anteroposterior. Read the result as a size, and a soft one. The cited reference notes that the ellipsoid formula underestimates the true volume by 10 to 18 percent in most glands, more so in large ones, which makes the figure well suited to following change across repeat scans and poorly suited to being read as an exact quantity. A typical adult gland is often quoted at around 20 to 30 mL and above roughly 30 mL is commonly called enlarged, but size climbs gradually with age and varies widely between individuals, so that is an orientation rather than a threshold. Enlargement is most often benign prostatic hyperplasia, and many cancers occur in normal-sized glands. This number replaces neither the measurement it comes from nor the finding a clinician makes.
Size on its own is not a finding
Enlargement is most often benign prostatic hyperplasia, which is very common with age, and many cancers occur in normal-sized glands. This page gives a size estimate, not a diagnosis.
An approximation, not a measurement
The cited reference notes that the ellipsoid formula underestimates the true volume by 10 to 18 percent in most glands, more so in large ones. It is reliable enough to follow change over time, but a single value carries that error with it.
Millimetres have to be divided by ten
Ultrasound and MRI reports often state the three diameters in millimetres. Divide each by 10 before entering centimetres here.
PSA density comes from the same number
Divide serum PSA in ng/mL by the volume this page returns: a PSA of 4.0 in a 33 mL gland gives about 0.12 ng/mL/cc. Values above roughly 0.15 are one factor among several that a urologist may weigh, never a result on their own.
Commonly misread
My volume is 45 mL, so something must be wrong with me.
Above roughly 30 mL is commonly described as enlarged, but that is an orientation rather than a threshold. Size rises gradually with age and varies a lot between individuals.
The number this page returns is the size of the gland.
It is a clinical approximation that underestimates the true volume by 10 to 18 percent in most glands. Use it to follow change, not as a measurement.
My report says 45 × 40 × 35, so I enter those three numbers.
Those are millimetres. Divide each by 10 and enter 4.5, 4.0 and 3.5 centimetres.
Reference table
| Length, width, height (cm) | Size note | Volume (mL) |
|---|---|---|
| 3, 3, 3 | below the usual adult range | 14.1 |
| 4, 3.5, 3 | within the usual range | 22.0 |
| 4, 4, 3 | within the usual range | 25.1 |
| 5, 4, 3 | around the enlargement mark | 31.4 |
| 4.5, 4, 3.5 | around the enlargement mark | 33.0 |
| 5, 4.5, 4 | enlarged | 47.1 |
| 6, 5, 4 | enlarged | 62.8 |
| 6, 5.5, 5 | markedly enlarged | 86.4 |
Questions
How is prostate volume calculated?
The gland is modelled as a prolate ellipsoid, so its volume is π/6 times length times width times height, with the three diameters in centimetres. The constant π/6 is about 0.52, which is why it is often called the 0.52 formula. A gland of 4.5 × 4.0 × 3.5 cm works out to roughly 33 mL.
Where do I find the three measurements?
They appear on a transrectal ultrasound or prostate MRI report, usually labelled as the longitudinal, transverse and anteroposterior diameters. If the report gives millimetres, divide by 10 before entering centimetres here. If it already states a volume, the calculation has been done for you.
What is a normal prostate volume?
A typical adult gland is often quoted at around 20 to 30 mL, and a volume above roughly 30 mL is commonly described as enlarged. Size increases gradually with age and varies a lot between individuals, so the range is an orientation rather than a threshold. Only a clinician can read your number in context.
How do I get PSA density from this?
Divide your serum PSA in ng/mL by the volume this page returns. A PSA of 4.0 in a 33 mL gland gives about 0.12 ng/mL/cc. Values above roughly 0.15 are one factor among several that a urologist may weigh — never a result on their own.
How accurate is the ellipsoid estimate?
It is a clinical approximation, not a measurement. The cited reference notes that the formula underestimates the true volume by 10 to 18 percent in most glands, more so in large ones. It is reliable enough to track change over time, but a single value carries that error with it.
Does a large prostate mean cancer?
No, and this page cannot answer that question at all. Enlargement is most often benign prostatic hyperplasia, which is very common with age, and many cancers occur in normal-sized glands. This is an educational tool, not a diagnosis — discuss your measurements and any symptoms with a urologist.
Sources and last check
Information, not medical advice.