Bladder Volume Calculator — Ultrasound Ellipsoid Formula
Enter the three ultrasound-measured dimensions of the bladder to estimate its volume in mL. The ellipsoidal formula (V = 0.52 × L × W × H) is the standard method used in clinical urology and nursing.
cm
cm
cm
Moderate — first urge likely
182 mL
volume- 1
Dimension product (L × W × H)
10 × 7 × 5 = 350 - 2
Bladder volume
0.52 × 350 = 1820.52 ≈ π/6, treating the bladder as a prolate ellipsoid.
How does this calculator work?
Bladder volume is estimated from ultrasound dimensions as V = 0.52 × L × W × H (mL), treating the bladder as an ellipsoid. Normal adult functional capacity is 400–600 mL; a post-void residual below 50 mL is normal. The formula is accurate to ±15–25% compared with catheter measurement.
Formula
How this is calculated
On bedside ultrasound the bladder is imaged in three planes and its longest (longitudinal, L), widest (transverse, W) and deepest (antero-posterior, H) diameters are recorded in centimetres. The validated formula V = 0.52 × L × W × H — where 0.52 ≈ π/6 — treats the bladder as a prolate ellipsoid, which closely approximates its actual shape at most fill levels. Because 1 mL = 1 cm³, the result is directly in millilitres.
Clinically, a post-void residual (PVR) below 50 mL is considered normal in most adults; 50–200 mL warrants monitoring; above 200–300 mL suggests urinary retention requiring evaluation. Normal functional capacity in adults is roughly 400–600 mL — the volume at which the urge to void becomes strong. Anatomical maximum capacity (with voluntary suppression) is typically 600–1 000 mL.
The formula is an estimate; accuracy varies with operator measurement consistency, bladder shape (which deviates from an ellipsoid at very low or high fill levels), and probe angle. Studies report ±15–25% accuracy compared with catheter-measured volumes. Dedicated 3-D portable bladder scanners apply more sophisticated averaging and are more accurate for clinical decisions.
Frequently asked questions
0.52 is the rounded value used in most clinical guidelines — the difference from π/6 is less than 0.1%, well within measurement uncertainty. Some protocols use 0.523 or 0.524; all give essentially identical results in practice.
Below 50 mL is generally normal for most adults. The 50–200 mL range is a clinical grey zone monitored over time. Above 200–300 mL is significant and may indicate incomplete emptying, urinary obstruction, or neurogenic bladder dysfunction.
For children the expected bladder capacity (mL) is often estimated as (age + 2) × 30 for ages 2–11. The ultrasound ellipsoid formula still measures actual fill volume accurately, but the normal ranges differ — consult paediatric references for age-specific PVR thresholds.
Also known as
TG we-Calculate Editorial Team. (2026). Bladder Volume Calculator — Ultrasound Ellipsoid Formula [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/bladder-volume-calculator
TG we-Calculate Editorial Team. "Bladder Volume Calculator — Ultrasound Ellipsoid Formula." TG we-Calculate. 2026. https://we-calculate.com/calculator/bladder-volume-calculator.
TG we-Calculate Editorial Team, "Bladder Volume Calculator — Ultrasound Ellipsoid Formula," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/bladder-volume-calculator
@misc{wecalculate_bladder_volume_calculator, title = {Bladder Volume Calculator — Ultrasound Ellipsoid Formula}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/bladder-volume-calculator}}, year = {2026}, note = {TG we-Calculate} }
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