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Weight-Based Infusion Rate Calculator

Convert a weight-based dose in mcg/kg/min, or mg/kg/h, and a drug concentration into a pump rate in mL per hour, with the hourly dose, as educational arithmetic.

Formula

rate (mL/h)=dose×W×601000×C(dose in mcg/kg/min, C in mg/mL)\text{rate}\,(\mathrm{mL/h}) = \dfrac{\text{dose}\times W\times 60}{1000\times C}\quad(\text{dose in mcg/kg/min, } C \text{ in mg/mL})
dose per hour (mg/h)=dose×W×601000\text{dose per hour}\,(\mathrm{mg/h}) = \dfrac{\text{dose}\times W\times 60}{1000}
dose\text{dose}
the ordered dose, per kilogram per minute
WW
the patient's weight, in kg
CC
drug per mL in the prepared solution

How it works

A weight-based dose is multiplied by the patient's weight to give a dose per minute; the factor 60 changes minutes to hours and 1,000 changes micrograms to milligrams. Dividing the dose per hour by the concentration of the solution gives the volume per hour, which is the rate the pump is set to.

Infusions of this kind are often of high-alert drugs, where a slip of a decimal point or a unit is harmful. The calculation here is arithmetic only, so check the order, the concentration and the units, use the pump's drug library where there is one, and have the result independently checked.

Worked example

An order of 5 mcg/kg/min for a 70 kg patient, from a solution of 1.6 mg/mL.

  1. Dose per minute = 5 × 70 = 350 mcg/min.
  2. Dose per hour = 350 × 60 / 1,000 = 21 mg/h.
  3. Rate = 21 / 1.6 = 13.125 mL/h.

The pump rate is 13.13 mL per hour, delivering 21 mg per hour.

These are the values the calculator opens with, so you can check its output against this example.

Assumptions

  • The weight and the concentration are correct and in the units stated.
  • A continuous infusion at a constant rate, with no loading dose.

Common mistakes

  • Mixing mcg and mg, or per minute and per hour.
  • Using the dosing weight when the order specifies another (for example ideal or adjusted).
  • Not verifying the calculation independently.

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Related equipment

Service documentation, failure modes and parts for the instruments this calculation is used with.