What is the urine output in mL/kg/h?
Enter the urine collected, the body weight, and the hours of collection to see the urine output in mL/kg/h and which KDIGO 2012 acute kidney injury criterion the average rate meets. For information only. This is not medical advice or a diagnosis. Do not use it to make treatment decisions without a clinician. No licensed clinician has reviewed this page.
- Urine output (mL/kg/h)
- 0.71
300 mL of urine over 6 hours at 70 kg is 0.71 mL/kg/h.
0.5 mL/kg/h or more
- Under 0.3 mL/kg/h
- 0.3 to under 0.5 mL/kg/h
- 0.5 mL/kg/h or more
- Urine output (mL/h)
- 50
- KDIGO 2012 urine output criterion
- Not under 0.5 mL/kg/h: does not meet a KDIGO urine output criterion
Urine output (mL/kg/h): 0.71. 300 mL of urine over 6 hours at 70 kg is 0.71 mL/kg/h.
Urine output (mL/kg/h)
This calculator gives general information only. It is not medical advice and does not replace a doctor or other health care provider. Talk with a professional about your results. Terms of use
How to calculate
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.
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.
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.
- 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
Each example is checked against the calculator on every build.
- Urine volume (mL) 300, Weight 70 kg, Collection time (hours) 6 gives Urine output (mL/kg/h) 0.71, Urine output (mL/h) 50, KDIGO 2012 urine output criterion 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/)
- Urine volume (mL) 240, Weight 80 kg, Collection time (hours) 8 gives Urine output (mL/kg/h) 0.38, Urine output (mL/h) 30, KDIGO 2012 urine output criterion Stage 1 criterion: under 0.5 mL/kg/h for 6 to 12 hours.
- Urine volume (mL) 400, Weight 70 kg, Collection time (hours) 12 gives Urine output (mL/kg/h) 0.48, Urine output (mL/h) 33.3, KDIGO 2012 urine output criterion Stage 2 criterion: under 0.5 mL/kg/h for 12 hours or more.
- Urine volume (mL) 300, Weight 50 kg, Collection time (hours) 24 gives Urine output (mL/kg/h) 0.25, Urine output (mL/h) 12.5, KDIGO 2012 urine output criterion Stage 3 criterion: under 0.3 mL/kg/h for 24 hours or more.
- Urine volume (mL) 0, Weight 70 kg, Collection time (hours) 12 gives Urine output (mL/kg/h) 0.00, Urine output (mL/h) 0, KDIGO 2012 urine output criterion Stage 3 criterion: anuria for 12 hours or more.
- Urine volume (mL) 100, Weight 70 kg, Collection time (hours) 4 gives Urine output (mL/kg/h) 0.36, Urine output (mL/h) 25, KDIGO 2012 urine output criterion Under 0.5 mL/kg/h, but for less than 6 hours: no KDIGO stage yet.
- Urine volume (mL) 420, Weight 70 kg, Collection time (hours) 12 gives Urine output (mL/kg/h) 0.50, Urine output (mL/h) 35, KDIGO 2012 urine output criterion Not under 0.5 mL/kg/h: does not meet a KDIGO urine output criterion.
- Urine volume (mL) 300, Weight 69.85 kg, Collection time (hours) 6 gives Urine output (mL/kg/h) 0.72, Urine output (mL/h) 50, KDIGO 2012 urine output criterion Not under 0.5 mL/kg/h: does not meet a KDIGO urine output criterion.
- Urine volume (mL) 249, Weight 100 kg, Collection time (hours) 10 gives Urine output (mL/kg/h) 0.25, Urine output (mL/h) 24.9, KDIGO 2012 urine output criterion Stage 1 criterion: under 0.5 mL/kg/h for 6 to 12 hours.
Medical disclaimer
This calculator is for information and education only. It is not medical advice, and its result is not a diagnosis. Do not use it to start, stop, or change a treatment without a clinician who knows your health history. No licensed clinician has reviewed this page. This site's editors checked the formulas and worked examples against published sources. If you think you have a medical emergency, call your local emergency number.
When this does not apply. The criteria are from the KDIGO 2012 acute kidney injury guideline. The guideline gives no separate urine output values for newborns, and this page is not meant for them. The urine output criterion is one of three ways to define AKI; the guideline also uses a rise in serum creatinine, which this page does not ask for, so the page gives the urine output criterion only, not a full AKI stage. In people with severe obesity the weight-based rate can flag AKI when the kidneys are normal, and collections without a catheter can miss urine. Volumes over 20,000 mL, weights outside 1 to 300 kg, or times outside 1 to 72 hours give no answer.
How it works
With the urine volume V in mL, the body weight W in kg, and the collection time t in hours:
- urine output = V ÷ (W × t) mL/kg/h, rounded once to 2 decimals (halves up);
- urine output per hour = V ÷ t mL/h, rounded once to 1 decimal (halves up).
A weight typed in pounds is read as exactly 0.45359237 kg per pound. The page works with the exact typed values and rounds once at the end.
The rate shown (2 decimals) and the exact hours typed are then compared with the urine output column of KDIGO 2012 Table 2, top row first. The first row that fits is the result, word for word:
| Check, in this order | Page text |
|---|---|
| volume is 0 and t is 12 or more | Stage 3 criterion: anuria for 12 hours or more |
| rate shown under 0.3 and t is 24 or more | Stage 3 criterion: under 0.3 mL/kg/h for 24 hours or more |
| rate shown under 0.5 and t is 12 or more | Stage 2 criterion: under 0.5 mL/kg/h for 12 hours or more |
| rate shown under 0.5 and t is 6 or more | Stage 1 criterion: under 0.5 mL/kg/h for 6 to 12 hours |
| rate shown under 0.5 (t under 6) | Under 0.5 mL/kg/h, but for less than 6 hours: no KDIGO stage yet |
| any other rate (0.50 or more) | Not under 0.5 mL/kg/h: does not meet a KDIGO urine output criterion |
So exactly 12 hours under 0.5 is stage 2 ("12 hours or more"), and exactly 6 hours is stage 1. A rate of 0.25 for 10 hours is stage 1, because the stage 3 rate needs 24 hours.
The rate also has a band: under 0.3, 0.3 to under 0.5, or 0.5 mL/kg/h or more, read from the rate shown.
Allowed input. Volume 0 to 20,000 mL, weight 1 to 300 kg (or the same in pounds), time 1 to 72 hours. Decimals are allowed.
Assumptions
- The volume is all the urine collected over the hours typed, so the rate is the average over that period. The guideline does not settle whether an average or a reduction lasting the whole period is meant.
- The weight is the one typed; the guideline does not choose between actual, ideal, and lean weight.
- The results are for education. They are not medical advice.
Worked examples by hand
300 mL, 70 kg, 6 hours (the page default). 300 ÷ (70 × 6) = 300 ÷ 420 = 0.714, shown as 0.71 mL/kg/h; 300 ÷ 6 = 50 mL/h. Not under 0.5: no criterion met.
240 mL, 80 kg, 8 hours. 240 ÷ 640 = 0.375, shown as 0.38; 30 mL/h. Under 0.5 for 8 hours: stage 1 criterion.
400 mL, 70 kg, 12 hours. 400 ÷ 840 = 0.476, shown as 0.48; 33.3 mL/h. Under 0.5 for 12 hours: stage 2 criterion.
300 mL, 50 kg, 24 hours. 300 ÷ 1,200 = 0.25; 12.5 mL/h. Under 0.3 for 24 hours: stage 3 criterion.
0 mL, 70 kg, 12 hours. 0.00 mL/kg/h. Anuria for 12 hours: stage 3 criterion.
100 mL, 70 kg, 4 hours. 100 ÷ 280 = 0.357, shown as 0.36; 25 mL/h. Under 0.5, but for less than 6 hours: no stage yet.
420 mL, 70 kg, 12 hours. 420 ÷ 840 = 0.50 exactly. Not under 0.5: no criterion met.
300 mL, 154 lb, 6 hours. 154 × 0.45359237 = 69.85322498 kg; 300 ÷ (69.85322498 × 6) = 0.7158, shown as 0.72; 50 mL/h.
249 mL, 100 kg, 10 hours. 249 ÷ 1,000 = 0.249, shown as 0.25; 24.9 mL/h. Under 0.3, but for 10 hours only, so the stage 3 rate row does not fit: stage 1 criterion.
Other questions people ask
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.