Measured Urine Output Rate Calculator (mL/hr & mL/kg/hr)

The submitted inputs are measured urine volume for one completed collection interval, elapsed time, and a body weight selected by an external protocol. Time is normalized to hours and weight to kilograms before the calculator reports average mL/hr and average mL/kg/hr.

It does not read an hourly time series, serum creatinine, fluid intake, net fluid balance, catheter status, laboratory data, a diagnosis, or a treatment input. None of those missing facts is inferred from the two arithmetic outputs.

The volume must represent the whole submitted interval, with start and end times that correspond to that volume. Combining a partial-interval volume with a full-interval duration changes both calculated averages. The confirmation records what the user submitted; it cannot prove that the physical collection or charting was complete.

Editing a number or changing a unit clears confirmation and old output. That behavior is a software safety measure against stale or silently reinterpreted results, not a clinical validation of the collection.

mL/hr is the absolute average flow over the submitted interval. mL/kg/hr adds the submitted kilogram weight as another denominator, so the same mL/hr produces different weight-normalized rates at different weights. They are related but not interchangeable quantities. This page does not decide which one a particular external protocol should use.

This page divides total volume by total time; it cannot reveal how urine was distributed within that interval. The same six-hour total could reflect steady output or several zero-output hours followed by a later concentrated volume. It cannot reconstruct missing hours or sliding windows.

Macedo compared urine-output criteria across different time aggregation approaches. Monard found that averaged and persistent definitions identified materially different proportions of patients; that was an observational comparison, not proof that one monitoring method causes a better outcome. [4, 5]

These are static guideline descriptions only. The calculator has no hourly series or serum creatinine and does not display Stage 1, 2, or 3; reaching an average does not automatically diagnose AKI.[1]

NICE describes urine output below 0.5 mL/kg/hr for more than 6 hours in adults and more than 8 hours in children and young people, alongside serum-creatinine criteria. This page does not collect age, choose an adult or pediatric pathway, or apply either duration dynamically.[3]

As of this page’s content date, the KDIGO 2026 AKI/AKD update is a public-review draft awaiting final publication and the first major update since 2012. A public-review draft is not a final guideline. This calculator implements no new automatic threshold or category from it; final publication would require a separate source review.[2]

Kilogram weight is directly in the mL/kg/hr denominator. Actual, admission, dry, ideal, adjusted, or another protocol-specific weight can differ, particularly with obesity or fluid shifts. Jiang reported that actual-weight normalization in obesity identified more AKI by urine criteria, but that observational result does not establish one universal best weight. Enter the weight named by the applicable external protocol; the page does not select it from BMI or diagnosis.[1, 8]

• Catheter kink, blockage, dislodgement, or leak.
• Missed void, retention, or obstruction.
• Bag-reading error or delayed charting.
• Diaper loss, evaporation, or contamination.
• Irrigation or another non-urine fluid in the recorded volume.
• Estimated or incomplete records.

Manual recording can be delayed and can overestimate output. Intensive monitoring has been associated with greater AKI detection and improved outcomes, but that observational association does not prove that one monitoring method caused the outcome difference.[6, 7]

A submitted 0 mL produces valid arithmetic of 0.0 mL/hr and 0.00 mL/kg/hr. Clinical anuria context requires a reliable complete collection and sufficient duration. A zero entry can also coexist with collection loss, obstruction, retention, catheter problems, or recording error. The page does not label anuria or decide urgency or management.[1, 7]

Diuretics, fluid administration, hemodynamics, obstruction, kidney function, and a changing clinical state can all affect urine output. This calculator has no fluid intake or net balance and cannot infer cause, volume status, or response to diuretics from the rate. It does not recommend starting, changing, or stopping treatment.[1, 3]

NICE uses a different duration for children and young people. Neonatal assessment uses modified neonatal KDIGO frameworks, and both serum creatinine and urine output have neonatal physiologic context. This page has no age, gestational age, or birth data, does not mix adult, pediatric, and neonatal standards, and emits no age-specific category.[3, 9]

• The collection is incomplete.
• Volume and duration do not describe the same interval.
• Weight comes from another time or protocol.
• Time or weight units are selected incorrectly.
• The catheter or collection system is compromised.
• Records are delayed, missing, or estimated.
• Fluid shifts or treatment are changing the monitored state.
• One interval average substitutes for an hourly series.
• The result substitutes for serum-creatinine assessment.
• An adult context is applied to a child or neonate.

• AKI diagnosis or AKI stage.
• Persistent oliguria or clinical anuria.
• The cause of low output.
• Obstruction or retention.
• Fluid status or response to diuretics.
• Serum-creatinine change.
• Fluid, diuretic, or catheter intervention.
• Dialysis, referral, admission, or another treatment.