Medical & Scientific Volume Calculators
Thirteen calculators built on published clinical and laboratory formulas — each one naming its source, showing its working, and stating plainly what it cannot tell you.
- ✓ Formulas cited on every page
- ✓ Reference ranges included
- ✓ Educational use only
Important: these calculators are educational tools. They implement published formulas correctly, but a number is not a diagnosis. Organ volumes and physiological parameters are interpreted in the context of your symptoms, history, imaging quality and other findings — none of which a calculator can see.
Never use these results to start, stop or change any treatment. If a result concerns you, take it to a qualified healthcare professional who can see the whole picture.
Organ volume from imaging
Most sonographic organ volumes use the prolate ellipsoid formula — three perpendicular diameters multiplied by a published coefficient.
- Prostate Volume Calculator
Ellipsoid formula with PSA density, the figure used alongside PSA in biopsy decisions.
- Bladder Volume Calculator
Bladder capacity and post-void residual, with the coefficients different scanners use.
- Thyroid Volume Calculator
Lobe-by-lobe using Brunn's coefficient, with goitre reference thresholds.
- Ovarian Volume Calculator
Ovarian and uterine volume, including the Rotterdam PCOS threshold.
- Spleen & Kidney Volume Calculator
Splenic and renal volume with splenomegaly reference ranges.
Physiological volumes
- Tidal Volume Calculator
Lung-protective ventilation from predicted body weight, following ARDSNet targets.
- Blood Volume Calculator
Total blood and plasma volume using Nadler's equation.
- Stroke Volume Calculator
LVOT VTI method, with cardiac output and stroke volume index.
Laboratory & scientific
- Column Volume Calculator
HPLC and chromatography column volume, void volume and dead time.
- Dilution Calculator
C₁V₁ = C₂V₂ for preparing solutions at a target concentration.
- Density, Mass & Volume Calculator
Solve for any of the three from the other two.
- Surface Area to Volume Ratio
The SA:V ratio behind cell size, heat loss and reaction rates.
- Volume of Revolution Calculator
Disk, washer and shell methods for solids of revolution.
The formula behind most of these: V = L × W × H × 0.52. Because π/6 ≈ 0.5236, multiplying three perpendicular diameters by roughly 0.52 gives the volume of a prolate ellipsoid — the shape most organs approximate. Individual organs use slightly different published coefficients, and each page names the one it applies and why.
Which formula each calculator uses
| Calculator | Formula | Source |
|---|---|---|
| Prostate | L × W × H × 0.52 | Prolate ellipsoid, standard in urological ultrasound |
| Bladder | L × W × H × 0.52 (or 0.7) | Ellipsoid; coefficient varies by scanner and protocol |
| Thyroid | Σ lobes × 0.479 | Brunn et al., 1981 |
| Ovarian | L × W × H × 0.523 | Ellipsoid; Rotterdam criteria for PCOS threshold |
| Spleen | L × W × H × 0.524 | Ellipsoid approximation |
| Tidal volume | 4–8 mL per kg PBW | ARDSNet / ARMA trial; Devine formula for PBW |
| Blood volume | Nadler equation | Nadler et al., 1962 |
| Stroke volume | LVOT area × VTI | Standard Doppler echocardiography |
| Column volume | π (d/2)² × L | Cylinder geometry; void fraction ≈ 0.65–0.70 |
| Dilution | C₁V₁ = C₂V₂ | Conservation of solute mass |
What these formulas can and cannot do
The ellipsoid formula assumes a smooth, regular, roughly egg-shaped organ. That assumption holds reasonably well for a normal prostate, thyroid lobe or ovary, and it is why the method became standard practice — it needs only three measurements from a routine scan.
It holds less well when the organ is irregular. A prostate with a large median lobe, a multinodular goitre, or a bladder distorted by a mass will all depart from a smooth ellipsoid, and the formula typically overestimates in those cases. Where precision matters, 3-D reconstruction or planimetry from cross-sectional imaging is more accurate — and considerably more work, which is why the three-diameter estimate remains in daily use.
Measurement quality dominates everything else. Because three diameters are multiplied together, a 10% error in each compounds to roughly a 33% error in the volume. Operator technique, probe angle and whether the true maximum diameter was captured matter more than the choice of coefficient.
How we handle medical content
Every calculator in this hub follows the same rules, set out in our editorial and accuracy policy:
- The formula is named and cited. You can see which published equation is being applied and check it against the source.
- The working is shown. Your numbers appear substituted into the formula, so the result is reproducible by hand.
- Reference ranges are labelled as such. Where we show a typical range, we say where it comes from and that ranges vary between populations, laboratories and guidelines.
- Nothing is framed as advice. No calculator here tells you what to do, what you have, or whether to be worried.
- Dates are visible. Each page shows when it was last reviewed, and we re-check pages when an underlying guideline changes.
If you find an error in a formula or a citation, please tell us — accuracy reports on these pages are handled ahead of everything else.
Frequently asked questions
Why do so many organ calculators use the same 0.52 coefficient?
Because it is π/6 ≈ 0.5236, the exact constant for an ellipsoid expressed through its three full diameters rather than its semi-axes. Organs like the prostate, ovaries and spleen are roughly ellipsoidal, and ultrasound produces three perpendicular measurements easily, so the same shortcut serves all of them. Sources round it to 0.52, 0.523 or 0.524; the difference is well under one percent.
How accurate are ellipsoid organ volume estimates?
Good for a regularly shaped organ, weaker for an irregular or nodular one. The important caveat is error compounding: because three measurements are multiplied together, a 10% error in each diameter produces roughly a 33% error in the volume. Where precision genuinely matters, cross-sectional imaging with 3-D reconstruction is the reference standard.
Can these calculators be used for diagnosis?
No. They are educational tools that reproduce published formulas so you can follow the arithmetic. A volume figure is one input among many, and thresholds vary between guidelines and populations. Any clinical decision belongs with a qualified professional who has the full picture.
Why is organ volume reported in millilitres, cubic centimetres and grams interchangeably?
One cubic centimetre equals one millilitre by definition, so those two are identical. Grams enter because soft tissue has a density very close to 1 g/cm³ — a 30 cm³ prostate weighs about 30 grams. Reports may use any of the three and mean effectively the same number.
Which calculator should I use for a partly filled organ or vessel?
The ellipsoid method assumes a filled, regularly shaped structure. For a spherical vessel holding liquid to a given depth, the correct geometry is a spherical cap rather than an ellipsoid — see the spherical cap calculator. Bladder volume is the common clinical exception, where a dedicated coefficient is applied to the filled bladder directly.