How this calculator works
Divide collected urine by body weight and observation hours. The balance is only recorded intake minus urine, so it omits stool, drains, insensible loss and other sources unless separately accounted for. Five percent of weight is reported as mass only, not as a fluid allowance. In adults, a low sustained output is part of AKI assessment, but an average over an interval cannot prove that a threshold was continuously met. Children need age-specific interpretation. The result is an estimate for information only and is not medical advice.
Formula
Urine output (mL/kg/hour) = urine volume in mL / (weight in kg × hours). Urine volume = rate × weight × hours. Partial balance = recorded intake - urine output over the same interval. Five percent body mass = 0.05 × weight.
Worked example
210 mL over 6 hours in a 70 kg adult gives 210 / (6 × 70) = 0.5 mL/kg/hour. With intake 500 mL, the partial balance is +290 mL. A 60 kg person producing 360 mL over 6 hours has a rate of 1.
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Frequently asked questions
Is a positive balance the same as fluid overload?
No. This partial balance omits other gains and losses, and fluid status requires clinical assessment.
Can urine output be zero?
Yes. Zero output gives a zero rate. It cannot uniquely recover weight or duration.
Does a rate at or above 0.5 exclude kidney injury?
No. AKI may occur with preserved urine output. Creatinine trends and the wider clinical picture remain important.