Ultrasound Bladder Volume
Enter bladder length, width, and height measurements to calculate volume using the prolate ellipsoid method (Factor 0.52).
Longitudinal plane (superior–inferior)
Transverse plane (side-to-side)
Anterior–posterior dimension
How to Use This Calculator
Acquire three orthogonal dimensions
Use ultrasound in longitudinal and transverse planes to measure bladder length, width, and height with calipers positioned at inner bladder wall.
Select consistent units
Enter values in centimetres or millimetres. The calculator automatically converts to compute the volume in millilitres.
Interpret the volume
Compare with clinical context: post-void residual, pre-procedural filling, retention symptoms, or neurogenic bladder assessments.
Formula
Volume (mL) = Length × Width × Height × 0.52
Measurements are in centimetres; multiply by 1000 to convert cubic centimetres to millilitres.
The 0.52 coefficient approximates the bladder to an ellipsoid shape.
Full Description
Bladder volume estimation via ultrasound is used for post-void residual assessment, monitoring urinary retention, and ensuring adequate filling before procedures. The prolate ellipsoid method (volume = L × W × H × 0.52) is widely adopted and correlates well with catheterised volumes. Accuracy depends on correct caliper placement and avoiding bladder compression. Always interpret results with patient symptoms, voiding history, and urodynamic data when available.
Frequently Asked Questions
How accurate is the ellipsoid method?
It generally estimates volume within 10–15% of catheterised volumes. Using multiple measurements and averaging improves precision.
Should I measure post-void residual immediately?
Yes. Perform ultrasound within 10 minutes of voiding to avoid refilling. A residual <50 mL is usually normal, while >200 mL may indicate urinary retention.
What if the bladder shape is irregular?
Complex shapes (e.g., diverticula, post-surgical bladders) reduce accuracy. Consider 3D ultrasound or catheterisation for precise measurement.
Can I use this calculator for paediatric patients?
Yes, but reference ranges differ by age. Interpret volumes relative to expected bladder capacity (age + 2) × 30 mL.