Urine Output Calculator
HealthCalculate urine output rate in mL per kg of body weight per hour from measured volume, body weight, and time period. An educational fluid balance reference tool.
Urine Output Rate
0.714
Total Rate (mL/hr)
50
What is a Urine Output Rate?
The Urine Output Calculator computes urine output rate in millilitres per kilogram of body weight per hour (mL/kg/hr) from a collected volume, body weight, and collection time period. This is a standard way to normalize urine output across people of different body sizes.
For related structural measurements, see the Bladder Volume Calculator.
How to use this Urine Output Rate calculator
- Enter the urine volume collected in millilitres.
- Enter the body weight in kilograms.
- Enter the collection period in hours.
- Read the Urine Output Rate (mL/kg/hr) and Total Rate (mL/hr) instantly.
Formula & Methodology
Rate (mL/hr) = Urine Volume ÷ Collection Hours Rate (mL/kg/hr) = Rate (mL/hr) ÷ Body Weight Worked example — 200 mL collected over 4 hours from a 70 kg person: Rate (mL/hr) = 200 ÷ 4 = 50 mL/hr Rate (mL/kg/hr) = 50 ÷ 70 = 0.71 mL/kg/hr
Frequently Asked Questions
Urine output rate expresses how much urine is produced relative to body weight over a given time period, typically measured in millilitres per kilogram per hour (mL/kg/hr). It's a common way to normalize urine output across people of different body sizes.
First the total volume is divided by the collection time to get a rate per hour, and then that hourly rate is divided by body weight to normalize it per kilogram, giving the final mL/kg/hr figure.
A given volume of urine means something different for a person weighing 50 kg versus 100 kg, so dividing by body weight allows for a more meaningful, size-independent comparison across different individuals.
Normalized urine output rate is a common reference figure in fluid balance monitoring, used alongside other clinical information to understand hydration and kidney function trends over time.
No — this calculator computes the rate only. Any interpretation of what a specific value means for a person's health should come from a qualified healthcare professional considering the full clinical context, not from this calculator alone.
This calculator works with any collection period you enter in hours; shorter, more frequent collection periods typically give a more responsive rate, while longer periods smooth out short-term fluctuations.
The same mL/kg/hr formula applies regardless of age, though normal reference ranges for urine output can differ between infants, children, and adults — this calculator computes the rate only, not an age-specific reference range.
The [Bladder Volume Calculator](/bladder-volume-calculator/) estimates how much urine is currently stored in the bladder from ultrasound measurements, while this calculator computes the rate of urine production over a collection period — two related but distinct measurements.
No — this calculator computes output rate only, based on volume collected, weight, and time. It does not factor in fluid intake, which would be needed for a complete fluid balance calculation.
This calculator uses millilitres for volume, kilograms for weight, and hours for time, producing a rate in mL/kg/hr, the standard unit for this type of calculation.
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