Bladder Volume Calculator
Compute bladder volume from three ultrasound diameters using the ellipsoid formula V = 0.52 × D1 × D2 × D3 — with post-void residual (PVR) interpretation and functional capacity estimates.
1 · Choose the measurement mode
2 · Enter the three diameters from the ultrasound
Formula used
The bladder is approximated as an ellipsoid. A full ellipsoid's volume is (4/3)π·a·b·c; with full diameters D = 2a, this becomes (π/6)·D1·D2·D3 ≈ 0.52 × D1 × D2 × D3. Since diameters are in cm and 1 cm³ = 1 mL, the result is directly in milliliters.
| Mode | Educational reference range | Meaning |
|---|---|---|
| PVR (after voiding) | < 50 mL | Normal |
| 50–200 mL | Borderline — needs monitoring | |
| > 200 mL | Abnormal — consult a doctor | |
| Capacity (full) | < 150 mL | Low |
| 150–550 mL | Typical (adults generally 300–500 mL) | |
| > 550 mL | High |
Note: clinical guidelines vary — some sources use 100 mL as the normal PVR threshold. The table above is a general reference range for education, not a diagnostic cutoff.
Worked examples (verified)
| Case | D1 × D2 × D3 | Calculation | Result |
|---|---|---|---|
| Adult PVR | 8 × 7 × 6 cm | 0.52 × 336 | 174.72 mL — borderline |
| Full capacity | 12 × 10 × 8 cm | 0.52 × 960 | 499.2 mL — typical |
| Small PVR | 5 × 4 × 3 cm | 0.52 × 60 | 31.2 mL — normal |
| Functional | 8 × 6 × 5 cm + voided 350 mL | 124.8 + 350 | 474.8 mL — typical |
Frequently asked questions (FAQ)
What is the formula for bladder volume from ultrasound?
The commonly used ellipsoid formula is V = 0.52 × D1 × D2 × D3, where D1, D2, and D3 are three mutually perpendicular diameters in centimeters. Because 1 cm³ = 1 mL, the result is directly in milliliters.
What is a normal post-void residual (PVR)?
Commonly used reference ranges: under 50 mL is considered normal, 50–200 mL is considered borderline (needs monitoring), and above 200 mL is considered abnormal. Clinical guidelines vary, however — some sources use 100 mL as the normal threshold. Results must be interpreted by a doctor.
What is functional bladder capacity?
Functional capacity is the volume of urine the bladder can actually hold, computed as the volume voided during urination plus the residual PVR. This calculator computes it automatically when you enter the voided volume.
What is the normal bladder capacity of an adult?
An adult bladder generally holds about 300–500 mL. This calculator uses a 150–550 mL reference range as “typical”; values below 150 mL are considered low and above 550 mL are considered high. This range varies between individuals and guidelines.
When should I use PVR mode versus capacity mode?
PVR mode is used for measurements taken right after urination — to assess residual urine. Capacity mode is used when the bladder is full before voiding — to assess maximum holding capacity.
How accurate is the 0.52 ellipsoid formula?
This formula is an estimate. The bladder is not always a perfect ellipsoid, and the accuracy of the diameter measurements taken by the operator affects the result. For clinical decisions, ultrasound results are read by a doctor or radiologist together with other findings.
Is this calculator’s result a medical diagnosis?
No. This calculator is purely an educational tool for understanding volume calculations from ultrasound. Classifications of normal, borderline, or abnormal are not a diagnosis — consult a doctor or urologist about your ultrasound results.
What units does this calculator use?
Diameters are entered in centimeters (cm) and volume results in milliliters (mL), because 1 cm³ equals 1 mL. Do not mix units — make sure all three diameters use the same unit.
Free tool by NRTechStudio