What this calculator does
Many structures seen on ultrasound (a thyroid nodule, an ovarian cyst, the uterus, a kidney) are roughly egg-shaped rather than a neat cube or sphere, so their volume is usually estimated by treating them as an ellipsoid: a 3D shape with three different radii. Given the length, width and height a sonographer measures on the scan, the standard formula multiplies the three together with a constant that accounts for the ellipsoid shape.
This calculator applies that same formula directly to three measurements, in centimetres, and reports the result in cubic centimetres, which is numerically the same as millilitres for soft tissue. It is a geometric estimate, not a diagnosis: how that number is interpreted for any specific case is a clinical judgement for the reporting sonographer or doctor.
The formula
Multiply length × width × height, then multiply by π/6 (approximately 0.523), the constant that converts a length-width-height box into the volume of the ellipsoid that fits inside it.
| Term | Meaning |
|---|---|
| Ellipsoid | A rounded 3D shape with three independent radii, used as a simplified stand-in for many organs and masses on ultrasound. |
| π/6 | The constant (about 0.523) that scales a length × width × height box down to the volume of an ellipsoid with those same three dimensions. |
The inputs explained
| Field | What to enter |
|---|---|
| Length (cm) | The longest measured dimension, in centimetres. |
| Width (cm) | The width measurement, perpendicular to length, in centimetres. |
| Height (cm) | The height (or depth) measurement, in centimetres. |
When to use it
Estimating a nodule or cyst volume
Taking the three measurements from an ultrasound report and finding the estimated volume, useful for tracking whether a nodule is growing or shrinking between scans.
Checking a reported volume
Recalculating a volume already stated on a report to confirm it follows the standard ellipsoid formula from the three measurements given.
Comparing scans over time
Running the same formula on measurements from different dates makes the change in estimated volume directly comparable, since it uses the same method each time.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How does estimated volume change with each measurement, from a 5 × 3 × 2.5 cm baseline?
The same width and height, with length varied to show how sensitive the volume is to each dimension.
| Length | Estimated volume |
|---|---|
| 3 cm | 11.78 cm³ (≈ mL) |
| 4 cm | 15.71 cm³ (≈ mL) |
| 5 cm | 19.63 cm³ (≈ mL) |
| 6 cm | 23.56 cm³ (≈ mL) |
| 7 cm | 27.49 cm³ (≈ mL) |
| 8 cm | 31.42 cm³ (≈ mL) |
Questions
Why π/6 and not just multiply the three numbers?
Multiplying length × width × height gives the volume of the box that exactly contains the shape, which is larger than the rounded ellipsoid actually sitting inside it. The constant π/6 (about 0.523) scales that box volume down to the ellipsoid's actual volume.
Is this the same formula doctors use?
Yes, this is the standard "ellipsoid formula" widely used in ultrasound reporting for estimating the volume of roughly oval structures from three measurements.
Does this tell me if a finding is normal or concerning?
No. This only performs the volume calculation from the numbers given. Interpreting what a given volume means for a specific person is a clinical judgement that belongs to the sonographer or doctor who performed and reviewed the scan.
What if the shape is very irregular?
The ellipsoid formula assumes a roughly oval shape. A highly irregular mass may need a different, often more specialised, volume estimation method, which a reporting clinician would use if relevant.
For the volume of a true geometric cone or sphere, see the cone volume calculator or a general sphere volume tool.