Whether you are estimating on the spot or checking a result somebody else gave you, the urine output calculator is the quickest way to get from fluid intake, time, urine volume and weight to five percent body weight, urine output rate and fluid balance.
What Is the Urine Output Calculator?
The urine output calculator gives you an estimate of five percent body weight, urine output rate and fluid balance based on fluid intake, time, urine volume and weight.
It is a quick reference figure rather than a diagnosis, and it is most useful for tracking how a number moves over time rather than for interpreting a single reading.
How the Urine Output Estimate Is Worked Out
The calculation follows published reference relationships, so it is a reasonable approximation when the inputs are accurate. It assumes an average adult and does not account for individual variation.
If you are comparing two people, or the same person over a period of weeks, keep the method and the inputs identical. A change in the method can easily look like a change in the person.
What This Calculator Does Not Do
It does not diagnose anything, and it does not replace advice from a clinician. If a figure comes out at an extreme, or if it differs sharply from what you expect, that is a reason to speak to a professional rather than to adjust the inputs.
Nothing you type here is stored or sent anywhere. The whole calculation happens in your browser.
A Worked Example
Working through an example, with fluid intake set to 10, time set to 5, urine volume set to 2, the calculator returns urine output rate of 0, and fluid balance of 8, and five percent body weight of -5,000. Substitute your own figures and the same steps produce the same kind of answer.
Frequently Asked Questions
What do I need to work out five percent body weight?
Enter fluid intake, time, urine volume and weight. The calculator then works through the relationship and reports five percent body weight, urine output rate and fluid balance.
What does the urine output actually calculate?
It takes fluid intake, time, urine volume and weight and converts them into five percent body weight, urine output rate and fluid balance using the standard relationship for this problem. Each step is applied in turn, so every output is traceable back to the numbers you typed in.
How should I enter fluid intake?
Use the value you actually have, in the unit shown next to the field. Enter every value in the same unit system. The calculator assumes the figures you supply are consistent, so it cannot correct a mistake that happens before the calculation starts.
Is the answer exact?
It is as exact as the formula and the inputs allow. The method itself is the standard one for this problem, so the only sources of error are the figures you enter and the precision you ask for.
Why does a small change in one value move the answer so much?
That happens when an output depends on a ratio, because dividing by a small number magnifies any change in it. Check the units first, then check whether the value you entered is in the range the relationship was designed for.