Bladder Volume Calculator

Estimate the urine volume held in the bladder from three ultrasound measurements using the ellipsoid formula, with results in mL, fluid ounces, and liters.

Quick Facts

Formula
Volume = 0.52 x Width x Height x Depth
The bladder is modeled as an ellipsoid; 0.52 approximates pi/6. Dimensions in cm give volume in mL.
Typical capacity
About 300-500 mL in adults
First urge near 150 mL; strong urge around 400-600 mL. General references, not diagnostic thresholds.

Your Results

Calculated
Bladder volume
-
Estimated urine volume (mL)
In fluid ounces
-
1 mL = 0.0338 US fl oz
In liters
-
Volume in mL divided by 1000
Reference category
-
Versus typical adult capacity

Ready

Enter the three bladder dimensions and press Calculate.

About the Bladder Volume Calculator

This calculator estimates the amount of urine held in the bladder from three ultrasound measurements. The bladder is modeled as an ellipsoid, so its volume is the product of its width, height, and depth multiplied by a shape coefficient. With all three dimensions entered in centimetres, the result comes out in cubic centimetres, which equal millilitres (mL) of urine.

The formula

The standard ellipsoid estimate is Volume = coefficient x Width x Height x Depth. The widely used coefficient is 0.52, a rounding of pi/6 (about 0.5236), the geometric factor for a prolate ellipsoid. Measure the three largest perpendicular diameters of the bladder: the transverse (width), the cranio-caudal (height), and the anterior-posterior (depth). A fuller, more rounded bladder is sometimes estimated with a higher coefficient such as 0.7.

How to get accurate results

  • Enter all three dimensions in the same unit (centimetres) and measure at the point of maximum diameter in each plane.
  • Keep the coefficient at 0.52 for the standard ellipsoid estimate unless a specific protocol tells you otherwise.
  • Bladder volume changes constantly with filling and voiding, so an estimate reflects only the moment of measurement.

Putting the result in context

A typical adult bladder holds roughly 300 to 500 mL, with a first urge to void near 150 mL and a strong urge around 400 to 600 mL. Measured just after urinating, the same three dimensions give the post-void residual (PVR). These are general population references, not diagnostic cut-offs, and normal values vary with age and sex.

When to consult a professional

This tool performs a geometric estimate only; it does not diagnose retention, obstruction, or any condition. For a result that concerns you, or for decisions about catheterization or treatment, consult a licensed healthcare provider who can interpret it alongside your clinical history.

Frequently Asked Questions

What formula does the bladder volume calculator use?
It uses the ellipsoid formula: Volume = coefficient x width x height x depth, with all three bladder diameters measured in centimetres. The standard coefficient is 0.52, which approximates pi/6 for a prolate ellipsoid. The result in cubic centimetres equals millilitres of urine.
What is a normal bladder capacity?
A typical adult bladder holds roughly 300 to 500 mL, with a first urge to void near 150 mL and a strong urge around 400 to 600 mL. Values vary with age, sex, and hydration, so treat any single estimate as a general reference rather than a diagnosis.
Why is 0.52 used as the coefficient?
The bladder is modelled as an ellipsoid, whose volume is pi/6 (about 0.5236) times the product of its three axes. Rounded to 0.52, this is the coefficient most widely used in bladder ultrasound. A fuller, more rounded bladder is sometimes estimated with a higher coefficient such as 0.7.
Can I use this to measure post-void residual?
Yes. Post-void residual (PVR) is bladder volume measured right after urinating, using the same width, height, and depth entered here. Interpreting PVR should be done with a clinician, since normal thresholds depend on age and clinical context.

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