Home›Calculators›Health›Urine Output Calculator

Urine Output Calculator

Health

Calculate urine output rate in mL per kg of body weight per hour from measured volume, body weight, and time. An educational fluid balance tool.

Reviewed by the thecalcu.com team · Last updated July 15, 2026

15,000
1200
0.548

Urine Output Rate

0.714
Total Rate (mL/hr)
50

This calculator computes your Urine Output Rate, Total Rate (mL/hr) from the values you enter.

Inputs
Urine Volume CollectedBody WeightCollection Period
Outputs
Urine Output RateTotal Rate (mL/hr)

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.

Why Use a Urine Output Calculator?

Comparing raw urine volumes across people of different sizes doesn't give a meaningful comparison on its own. Normalizing by body weight and time gives a standardized rate that's easier to track and compare, and this calculator automates that two-step calculation instantly.

Who Should Use This Calculator?

  • Students of nursing or physiology learning how urine output rate is calculated and normalized.
  • Healthcare educators demonstrating fluid balance calculation methodology.
  • Anyone reviewing a fluid balance chart who wants to reproduce or verify a stated rate.
  • Researchers working with urine output data across different body sizes.

What Insights Does the Urine Output Calculator Give You?

The Urine Output Rate in mL/kg/hr is the headline, weight-normalized result. The Total Rate (mL/hr) shows the un-normalized hourly rate before dividing by body weight, useful as an intermediate reference figure.

How to use this Urine Output Rate calculator

  1. Enter the urine volume collected in millilitres.
  2. Enter the body weight in kilograms.
  3. Enter the collection period in hours.
  4. Read the Urine Output Rate (mL/kg/hr) and Total Rate (mL/hr) instantly.
Show formula & methodology ↓Show less ↑

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

What is urine output rate?
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.
How is urine output rate calculated?
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.
Why normalize urine output by body weight?
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.
What is this calculation commonly used for?
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.
Is a specific mL/kg/hr threshold a diagnosis?
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.
What collection period should I use?
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.
Can this calculator be used for pediatric patients?
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.
What is the difference between this and the Bladder Volume Calculator?
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.
Does this calculator account for fluid intake?
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.
What units does this calculator use?
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.
Also known as
urine output rate calculatormL per kg per hour calculatorfluid balance calculatoroliguria calculator