# What is the urine output in mL/kg/h?

Works out urine output in mL/kg/h from the volume collected, the body weight, and the hours, and compares it with the KDIGO 2012 urine output criteria for acute kidney injury.

- Page: https://www.acalculator.org/health/urine-output-calculator
- JSON spec: https://www.acalculator.org/health/urine-output-calculator.json
- Version: 1fcc2a56b129

## Default answer

Example with the default inputs (Urine volume (mL) 300, Weight 70 kg, Collection time (hours) 6): 300 mL of urine over 6 hours at 70 kg is 0.71 mL/kg/h.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| volume | Urine volume (mL) | The urine collected over the whole period, 0 to 20,000 mL. |
| weight | Weight | Body weight, from 1 kg to 300 kg. |
| hours | Collection time (hours) | The hours over which the urine was collected, 1 to 72. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| rate | Urine output (mL/kg/h) | Volume ÷ (weight in kg × hours), to 2 decimals. |
| perHour | Urine output (mL/h) | Volume ÷ hours, to 1 decimal. |
| stage | KDIGO 2012 urine output criterion | Which urine output criterion of KDIGO 2012 Table 2 the average rate over this period meets. |

## Method

Urine output (mL/kg/h) = volume (mL) ÷ (weight (kg) × hours), rounded once to 2 decimals, halves up; the rounded rate and the hours are compared with the KDIGO 2012 urine output criteria.

## Assumptions

- The volume is all the urine collected over the hours typed, so the rate is the average over that period.
- The weight is the body weight typed (KDIGO 2012 does not say which weight to use).
- The criteria are for adults and children; newborns are not covered by this page.

## Worked examples

1. volume = 300, weight = 70, hours = 6 gives rate = 0.71, perHour = 50, stage = Not under 0.5 mL/kg/h: does not meet a KDIGO urine output criterion. Source: KDIGO 2012 AKI guideline, recommendation 2.1.1 (https://pmc.ncbi.nlm.nih.gov/articles/PMC4089595/).
2. volume = 240, weight = 80, hours = 8 gives rate = 0.38, perHour = 30, stage = Stage 1 criterion: under 0.5 mL/kg/h for 6 to 12 hours.
3. volume = 400, weight = 70, hours = 12 gives rate = 0.48, perHour = 33.3, stage = Stage 2 criterion: under 0.5 mL/kg/h for 12 hours or more.
4. volume = 300, weight = 50, hours = 24 gives rate = 0.25, perHour = 12.5, stage = Stage 3 criterion: under 0.3 mL/kg/h for 24 hours or more.
5. volume = 0, weight = 70, hours = 12 gives rate = 0.00, perHour = 0, stage = Stage 3 criterion: anuria for 12 hours or more.
6. volume = 100, weight = 70, hours = 4 gives rate = 0.36, perHour = 25, stage = Under 0.5 mL/kg/h, but for less than 6 hours: no KDIGO stage yet.
7. volume = 420, weight = 70, hours = 12 gives rate = 0.50, perHour = 35, stage = Not under 0.5 mL/kg/h: does not meet a KDIGO urine output criterion.
8. volume = 300, weight = 69.853225, hours = 6 gives rate = 0.72, perHour = 50, stage = Not under 0.5 mL/kg/h: does not meet a KDIGO urine output criterion.
9. volume = 249, weight = 100, hours = 10 gives rate = 0.25, perHour = 24.9, stage = Stage 1 criterion: under 0.5 mL/kg/h for 6 to 12 hours.

## FAQ

### How do I calculate urine output in mL/kg/h?

Divide the urine volume in mL by the body weight in kg, then by the hours of collection. For 240 mL over 8 hours in an 80 kg adult: 240 ÷ 80 ÷ 8 = 0.375, shown as 0.38 mL/kg/h.

### What urine output counts as low?

The KDIGO 2012 guideline on acute kidney injury (AKI) counts a urine volume under 0.5 mL/kg/h for 6 hours as one way to define AKI. It is one of three criteria; the other two use a rise in serum creatinine.

### What are the KDIGO urine output stages?

KDIGO 2012 Table 2: stage 1 is under 0.5 mL/kg/h for 6 to 12 hours; stage 2 is under 0.5 mL/kg/h for 12 hours or more; stage 3 is under 0.3 mL/kg/h for 24 hours or more, or anuria (no urine) for 12 hours or more. The full staging also uses serum creatinine, which this page does not ask for.

### Which weight should I use?

The guideline does not say. It lists actual weight, ideal body weight, and lean body mass as a question for research, and warns that in people with severe obesity the weight-based criterion can flag AKI when the kidneys are normal. This page uses the weight you type.

### Does the page check every hour?

No. It uses the average over the period you type. KDIGO 2012 says it is not known whether the urine criteria should be applied to an average or to a reduction that lasts the whole period, so an average under 0.5 can hide hours above it, and the other way round.

### Why does the stage need 6 hours?

Because the KDIGO criterion is a low urine output that lasts. Under 0.5 mL/kg/h for less than 6 hours meets no criterion yet; the page says so.

### How accurate is a urine output measurement?

KDIGO 2012 notes that urine collections can be inaccurate, mostly in people without a urinary catheter. A missed void lowers the measured volume and the rate.

## Sources

- Kidney Disease: Improving Global Outcomes (KDIGO) Acute Kidney Injury Work Group. KDIGO Clinical Practice Guideline for Acute Kidney Injury. Section 2: AKI Definition. Kidney Int Suppl. 2012;2(1):19-36 (recommendation 2.1.1: urine volume under 0.5 ml/kg/h for 6 hours; Table 2, staging of AKI, urine output column; text on weight, obesity, averaging, and collection accuracy). https://doi.org/10.1038/kisup.2011.32 (full text: https://pmc.ncbi.nlm.nih.gov/articles/PMC4089595/, retrieved 2026-10-19)