Ultrasound Bladder Volume Calculator
Enter the three bladder dimensions measured on ultrasound (in centimeters). The calculator uses the standard ellipsoid estimate:
Volume (mL) = Length × Width × Height × Correction Factor
Educational use only. This tool does not diagnose urinary retention, obstruction, or infection. Clinical decisions should be made by a licensed professional.
What is bladder volume?
Bladder volume is the estimated amount of urine inside the bladder at a specific point in time. In clinics and hospitals, this is often measured using ultrasound to help evaluate symptoms such as urinary frequency, urgency, difficulty urinating, incontinence, or suspected urinary retention.
A common scenario is measuring post-void residual (PVR) volume, which is the amount of urine left after urination. High PVR can be associated with incomplete emptying and may need medical evaluation.
Formula used by this calculator
This calculator uses the widely accepted ellipsoid approximation:
Volume (mL) = Length (cm) × Width (cm) × Height (cm) × 0.52
- Length: superior-inferior bladder dimension
- Width: transverse dimension
- Height: anterior-posterior dimension
- 0.52: geometric correction for ellipsoid shape
Because 1 cubic centimeter equals 1 milliliter, the result naturally comes out in mL.
How to use the calculator correctly
Step-by-step
- Measure bladder dimensions on ultrasound in centimeters.
- Enter length, width, and height values.
- Keep correction factor at 0.52 unless your protocol differs.
- Optionally enter voided volume to estimate total pre-void bladder volume and residual percentage.
- Click Calculate Volume.
Optional residual interpretation
If you enter a voided volume, this page estimates:
- Estimated pre-void volume = residual measured volume + voided volume
- Residual percentage = residual / pre-void volume × 100%
Reference ranges and context
Interpretation depends on age, hydration status, symptoms, and timing. The values below are rough educational references, not strict diagnostic cutoffs.
| Estimated bladder volume (mL) | General context |
|---|---|
| < 50 | Very low volume, often near-empty bladder |
| 50–150 | Low fill |
| 150–300 | Moderate fill |
| 300–500 | Full bladder range for many adults |
| > 500 | Very full/distended in many situations |
Pediatric expected bladder capacity
For children, a commonly cited estimate for expected capacity is:
Expected capacity (mL) = (Age in years + 2) × 30
This can provide useful perspective, but pediatric urology decisions should never rely on one number alone.
Common sources of error
- Measuring one or more dimensions off-axis
- Wrong unit entry (mm instead of cm)
- Using the wrong correction factor for your institution
- Bladder shape distortion from nearby structures or probe pressure
- Delay between voiding and measurement
Clinical reminders
Bladder volume is a useful data point, but care should integrate symptoms, physical examination, urinalysis, medications, neurologic status, and other imaging when needed. Persistent urinary retention, painful inability to void, fever, hematuria, or severe lower abdominal pain should receive prompt medical attention.
FAQ
Is this calculator only for clinicians?
No. Anyone can use it for educational estimation. Still, interpretation should be done by a healthcare professional.
Why are there different correction factors?
Different scanners and protocols may use slightly different geometric assumptions. The 0.52 factor is a standard ellipsoid estimate and is the default here.
Can this tool diagnose urinary retention?
No. It estimates volume only. Diagnosis requires clinical evaluation and, when appropriate, repeat measurements and additional tests.