Urine Output Calculator — mL/kg/hr Clinical Rate
Enter the total urine volume collected, the patient's weight, and the observation period to get the weight-adjusted urine output rate in mL/kg/hr — the standard clinical measure used to assess kidney perfusion and fluid balance.
mL
kg
hours
Normal (0.5–1.0 mL/kg/hr)
- 1
Weight × time
70 × 8 = 560 - 2
Urine output rate
500 ÷ 560 = 0.89Dividing total volume by the weight-time product normalises for patient size and collection duration.
How does this calculator work?
Urine Output (mL/kg/hr) = Volume (mL) ÷ (Weight kg × Hours). Normal adult range: 0.5–1.0 mL/kg/hr. Oliguria (< 0.5 mL/kg/hr for ≥ 6 hr) may indicate AKI or haemodynamic compromise. Polyuria (> 3 mL/kg/hr) may suggest DI, hyperglycaemia, or recovery-phase AKI.
Formula
How this is calculated
Urine output reflects kidney perfusion and the body's fluid balance. In clinical settings, urine is collected via a Foley catheter or measured voiding and expressed as a weight-adjusted hourly rate. The formula divides total collected volume by the product of body weight and the observation period: UO (mL/kg/hr) = Volume ÷ (Weight × Hours). This normalises for patient size and collection duration.
The internationally accepted adult thresholds are: anuria (< 0.1 mL/kg/hr), oliguria (< 0.5 mL/kg/hr), normal (0.5–1.0 mL/kg/hr), elevated (1.0–3.0 mL/kg/hr), and polyuria (> 3 mL/kg/hr). Oliguria is a key early sign of acute kidney injury (AKI), haemodynamic compromise, or inadequate fluid resuscitation, and is one of the KDIGO criteria for staging AKI. Polyuria can indicate diabetes insipidus, hyperglycaemia, recovering AKI, or excessive fluid administration.
This calculator uses actual body weight. In morbidly obese patients some protocols use ideal body weight to avoid underestimating output; consult your unit's guideline. The result does not replace clinical assessment — trends over time matter more than any single value, and output must be interpreted alongside vital signs, fluid balance, creatinine, and the clinical picture.
Frequently asked questions
A normal adult urine output is 0.5–1.0 mL/kg/hr (roughly 30–60 mL/hr for a 70 kg patient). Sustained output below 0.5 mL/kg/hr for 6 or more hours meets the KDIGO definition of oliguria and warrants clinical evaluation.
Oliguria is a urine output < 0.5 mL/kg/hr. KDIGO 2012 defines oliguria persisting ≥ 6 hours as Stage 1 AKI. Common causes include hypovolaemia, sepsis, heart failure, urinary obstruction, and nephrotoxins. Prompt assessment of cause and fluid status is essential.
Most protocols and reference ranges use actual body weight, which this calculator applies. Some centres use ideal body weight (IBW) or adjusted body weight for obese patients, since excess adipose tissue has lower fluid content. Check your institution's protocol; for non-obese patients the difference is negligible.
Also known as
TG we-Calculate Editorial Team. (2026). Urine Output Calculator — mL/kg/hr Clinical Rate [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/urine-output-calculator
TG we-Calculate Editorial Team. "Urine Output Calculator — mL/kg/hr Clinical Rate." TG we-Calculate. 2026. https://we-calculate.com/calculator/urine-output-calculator.
TG we-Calculate Editorial Team, "Urine Output Calculator — mL/kg/hr Clinical Rate," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/urine-output-calculator
@misc{wecalculate_urine_output_calculator, title = {Urine Output Calculator — mL/kg/hr Clinical Rate}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/urine-output-calculator}}, year = {2026}, note = {TG we-Calculate} }
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