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Calculators · Weight-based infusion

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Weight-based infusion calculator

Convert an ordered mcg/kg/min rate into a pump setting in mL/hr. See the mcg/kg/min formula for the method.

Pump rate

13.1 mL/hr
1. Find the bag concentration in mcg/mL
400 mg × ( 1000 mcg ÷ 1 mg ) ÷ 250 mL
= 1600 mcg/mL
2. Dose per minute: multiply the rate by the patient's weight
5 mcg/kg/min × 70 kg
= 350 mcg/min
3. Convert to mcg per hour
350 mcg/min × ( 60 min ÷ 1 hr )
= 21000 mcg/hr
4. Divide by concentration so mcg cancels, leaving mL/hr
21000 mcg/hr × ( 1 mL ÷ 1600 mcg )
= 13.1 mL/hr

How it works

This is the capstone four-step dimensional-analysis problem:

1. Concentration (mcg/mL) = drug (mg) × 1000 ÷ bag volume (mL)
2. Dose (mcg/min) = ordered rate (mcg/kg/min) × weight (kg)
3. Dose (mcg/hr) = mcg/min × 60
4. Pump rate (mL/hr) = mcg/hr ÷ concentration (mcg/mL)

The full method, with practice problems, is in the weight-based IV infusion lesson.

Worked example

A patient weighing 70 kg has dopamine 400 mg in 250 mL. The prescriber orders 5 mcg/kg/min. What pump rate (mL/hr) delivers this order?

Answer: 13.1 mL/hr
1. Find the bag concentration in mcg/mL
400 mg × ( 1000 mcg ÷ 1 mg ) ÷ 250 mL
= 1600 mcg/mL
2. Dose per minute: multiply the rate by the patient's weight
5 mcg/kg/min × 70 kg
= 350 mcg/min
3. Convert to mcg per hour
350 mcg/min × ( 60 min ÷ 1 hr )
= 21000 mcg/hr
4. Divide by concentration so mcg cancels, leaving mL/hr
21000 mcg/hr × ( 1 mL ÷ 1600 mcg )
= 13.1 mL/hr

Frequently asked questions

What is the mcg/kg/min to mL/hr formula?

Pump rate (mL/hr) = ordered rate (mcg/kg/min) x weight (kg) x 60 (min/hr) divided by the bag concentration (mcg/mL). The concentration is the drug amount in mg x 1000 divided by the bag volume in mL.

Why do I multiply the drug amount by 1000?

The order is written in micrograms but the bag is labeled in milligrams. Converting mg to mcg (1 mg = 1000 mcg) makes the units match so they cancel correctly.

Which drugs are ordered in mcg/kg/min?

Titrated critical-care infusions such as dopamine, dobutamine, and nitroprusside are commonly ordered in mcg/kg/min. Always confirm the order and your facility's titration policy.