Urine Output Calculator

Created by Łucja Zaborowska, MD, PhD candidate
Reviewed by Bogna Szyk and Jack Bowater
Last updated: Jun 15, 2022

Our urine output calculator will show you an easy way of performing daily urine output calculations. Our tool will equip you with your patient's fluid balance and urine output in ml/ kg/ hr.

In the article below, we'll talk about the value of normal urine output per hour, dehydration, and the total body water volume. We'll also teach you how to calculate urine output in ml/ kg/ hr. 💧

How to use the urine output calculator?

To calculate the urine output rate, you'll need the following data:

  1. Your patient's age;

  2. Your patient's weight;

  3. The period of time over which the urine was collected;

  4. The urine output - the volume of urine collected during the given period of time;

  5. Your patient's fluid intake during the given period of time; and

  6. It's ready! Our calculator will supply you with both the fluid balance and the urine output rate of your patient! 🚰

    • You will get a notification if your patient's urine output per hour is indicative of acute kidney injury.

    • Our calculator will let you know if your patient suffers from oliguria (peeing less than usual) or polyuria (passing water way too often).

Now it's time to go one step further:

How to calculate urine output in ml/kg/hr?

If you want to be better than our ml/ kg/ hr calculator, you need to practice! Follow our detailed instruction and the urine output calculation examples:

  1. Collect your patient's weight, age, urine output, and the period over which the urine was collected. Our patient is 20 years old, weighs 80 kg, and we collected 3L (3000 mL) of urine during a 24-hours observation period.

  2. Use the following equation to compute how much urine is output per hour:

    Urine output (ml/kg/hr) = Collected urine / (Weight * Time)

Where,

  • Weight is given in kilograms (kg);
  • Collected urine is given in milliliters (mL); and
  • Time is given in hours

Our patient's data:

x = 3000 / (80 * 24) = 3000 / 1920

x = 1.56 ml/kg/hr

  1. Use the patient's age to determine if the urine output is within the normal range.

Check our table with the values of urine output characteristic for a healthy person, and someone with poly/oliguria.

Our patient's over 18 years old - his urine output is 1.56 ml/kg/hr, which is within the normal range.

Hey, well done! 🎉

Fluid balance

Fluid balance informs you whether your patient maintains their total body water volume. It allows you to correct the fluid intake, both orally and intravenously. In case of dehydration, the fluid balance's value is negative. A regular person experiences symptoms of dehydration after the loss of around 7% of their total body water or 5% of their weight.

Fluid balance = Fluid intake - Collected urine

All of the variables are given in milliliters (mL).

You can also check:

💡 Remember that your patient may lose significant amounts of water though their lungs, skin and stool - especially when their body temperature is elevated.

What's the normal hourly urine output?

What's the minimum urine output per hour for healthy adults and children? Find out with one of the tables below!

For adults (≥18 years old)

Urine output (ml/kg/h)

Meaning

<0.5

Oligouria

0.5-5

Healthy person

>5

Polyuria

For children (<18 years old)

Urine output (ml/kg/h)

Meaning

<1

Oligouria

1-3

Healthy person

>3

Polyuria

FAQ

How to calculate urine output for a 70 kg patient?

In order to do that, we need a bit more information:

  • The amount of urine collected; and
  • The time over which the urine was collected.

Then we may use the following equation:

Urine output (ml/kg/hr) = Collected urine / (Weight * Time)

Let's say that we gathered 300 ml of urine during a 6-hours observation.

Urine output (ml/kg/hr) = 300 ml / (70 kg * 6 hr)

Urine output (ml/kg/hr) = 0.71

What's the minimum urine output per hour?

A healthy urine output for an adult person should be greater than or equal to 0.5 ml/kg/hr. This minimum value is a bit different for children (<18 years old), which is 1 ml/kg/hr.

How do we measure urine output?

We can measure the urine output by inserting a Foley catheter into one's bladder. The catheter is a long tube that allows us to collect urine into the attached container. Then we can easily measure the amount of urine collected during the given time.

We may also calculate the urine output per hour using the following equation:

Urine output (ml/kg/hr) = Collected urine / (Weight * Time)

Łucja Zaborowska, MD, PhD candidate
Your patient's age:
≥18 years
Weight
lb
Time
hrs
Urine volume
ml
Fluid intake
ml
Results
Urine output rate
ml/
kg
/hr
Fluid balance
ml
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