Infusion Rate Calculator
Weight-based continuous IV infusions are ordered in mcg/kg/min (or mg/kg/hr), but IV pumps are programmed in mL/hr. Converting between these units requires knowing the patient weight, the dose ordered, and the concentration of the drug in the infusion bag. The formula is: Rate (mL/hr) = Dose (mcg/kg/min) x Weight (kg) x 60 / Concentration (mcg/mL). This conversion is essential for safe administration of vasoactive drugs, inotropes, and other critical care infusions.
Infusion rate formula
Rate (mL/hr) = Dose (mcg/kg/min) x Weight (kg) x 60 / Concentration (mcg/mL)
The factor 60 converts minutes to hours. Concentration = drug mass / volume (e.g., mg to mcg by multiplying by 1,000 then dividing by volume in mL). Always double-check the concentration units match the dose units.
Common weight-based infusion drugs
- Dopamine: typical range 2 to 20 mcg/kg/min; renal and vasopressor effects vary by dose range.
- Dobutamine: typical range 2 to 20 mcg/kg/min; positive inotrope.
- Norepinephrine: typically 0.01 to 3 mcg/kg/min; potent vasopressor.
- Milrinone: loading and maintenance in mcg/kg/min; used in heart failure.
- Nitroprusside: typical 0.3 to 10 mcg/kg/min; vasodilator (cyanide toxicity risk at high rates).
Infusion rate calculator: frequently asked questions
How is infusion rate calculated from mcg/kg/min?
Infusion rate (mL/hr) = Dose (mcg/kg/min) x Weight (kg) x 60 (min/hr) / Concentration (mcg/mL). This converts weight-based per-minute dosing to the volume per hour that an IV pump delivers.
What is drug concentration in an infusion?
Drug concentration is the amount of drug dissolved in the infusion fluid, expressed as mcg/mL or mg/mL. For example, dopamine 400 mg in 250 mL gives a concentration of 1,600 mcg/mL.
Why is infusion rate expressed in mL/hr?
IV pumps are programmed in mL/hr because this is the volumetric flow rate they control. Converting weight-based mcg/kg/min orders to mL/hr is a critical nursing and pharmacy calculation performed before starting any weight-based infusion.
What drugs are commonly dosed in mcg/kg/min?
Vasopressors and inotropes including dopamine, dobutamine, norepinephrine, and epinephrine are commonly ordered in mcg/kg/min. Vasodilators such as nitroprusside and milrinone are also weight-based per-minute infusions.
Can this calculator be used for clinical practice?
This tool is for educational and informational purposes only. All IV infusion calculations in clinical settings must be independently verified by qualified nursing and pharmacy staff using validated institutional processes.
Official sources
- U.S. Food and Drug Administration: FDA Drugs Information.
- NIH National Library of Medicine: Pharmacokinetics (StatPearls).
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.