How do you convert mcg/kg/min to mL/h?
Work out the concentration in mcg/mL, then multiply dose × weight × 60 and divide by that concentration. Weight-based infusions, typical of vasoactive drugs in critical care, are prescribed in micrograms per kilogram per minute. The pump is set in mL/h, so you need three things to link them: the dose, the weight and the concentration.
First the concentration, in micrograms per mL:
Concentration (mcg/mL) = Drug (mg) × 1000 ÷ Total volume (mL)
Then the pump rate:
Rate (mL/h) = Dose (mcg/kg/min) × Weight (kg) × 60 ÷ Concentration (mcg/mL)
To go the other way, from a running rate to the dose being delivered: Dose (mcg/kg/min) = Rate (mL/h) × Concentration (mcg/mL) ÷ (Weight (kg) × 60).
If the mg-to-mcg step is where you hesitate, the medication unit conversions guide covers it with examples.
How to use the calculator
- In I want to find, choose “Pump rate (mL/h) from a dose” or “Dose (mcg/kg/min) from a pump rate”.
- Enter the Drug in the bag or syringe in mg and the Total volume in mL, as written on the label of the prepared infusion.
- Enter the Weight in kg.
- Enter the Dose rate in mcg/kg/min, or the Pump rate in mL/h, depending on the mode.
- Read the result and check the concentration in the first step of the working.
Worked examples
Example 1 – dose to pump rate. 400 mg in 250 mL, a 70 kg patient, 5 mcg/kg/min prescribed. Concentration: 400 × 1,000 ÷ 250 = 1,600 mcg/mL. Rate: 5 × 70 × 60 ÷ 1,600 = 13.125, shown as 13.13 mL/h. Drug delivered: 21 mg per hour.
Example 2 – pump rate to dose. Same bag (1,600 mcg/mL), an 80 kg patient, the pump running at 15 mL/h. 15 × 1,600 ÷ (80 × 60) = 5 mcg/kg/min.
Example 3 – a dilute syringe. 4 mg in 50 mL, an 80 kg patient, 0.1 mcg/kg/min. Concentration: 4 × 1,000 ÷ 50 = 80 mcg/mL. Rate: 0.1 × 80 × 60 ÷ 80 = 6 mL/h. Drug delivered: 0.48 mg per hour.
To check the concentration of a bag you made up yourself, the IV bag concentration calculator does that step on its own.
Quick reference
Pump rate in mL/h at 1,600 mcg/mL (for example 400 mg in 250 mL), to two decimal places as the calculator shows it.
| Dose | 50 kg | 70 kg | 90 kg |
|---|---|---|---|
| 2 mcg/kg/min | 3.75 | 5.25 | 6.75 |
| 5 mcg/kg/min | 9.38 | 13.13 | 16.88 |
| 10 mcg/kg/min | 18.75 | 26.25 | 33.75 |
| 15 mcg/kg/min | 28.13 | 39.38 | 50.63 |
| 20 mcg/kg/min | 37.5 | 52.5 | 67.5 |
The rate is directly proportional to dose and weight: double either and the mL/h doubles. Halve the concentration and the mL/h also doubles. Which weight goes in the formula is a protocol decision; the guide to actual, ideal and adjusted body weight explains the options.
Common mistakes
- Leaving the drug in mg. The concentration must be in mcg/mL. Without the × 1,000 the rate comes out a thousand times too high.
- Forgetting the × 60. Without it you get a rate per minute, sixty times too low for a pump set in mL/h.
- Confusing mcg/kg/min with mcg/min or mcg/kg/h. Each needs a different formula. It’s worth checking the units on the prescription first.
- Using the wrong total volume. Enter the final volume of the prepared solution (the bag or syringe as made up), not only the diluent added.
A quick sense check
Many weight-based infusions run at a few mL/h up to a few tens of mL/h. A result in the hundreds, or well under 1 mL/h, usually points to a missing × 1,000 or × 60. These are often high-alert medicines, so we recommend matching the numbers to the prescription and product information, and having them double-checked independently.
Frequently asked questions
What is the formula to convert mcg/kg/min to mL/h?
mL/h = dose (mcg/kg/min) × weight (kg) × 60 ÷ concentration (mcg/mL). For 5 mcg/kg/min, 70 kg and 1,600 mcg/mL: 5 × 70 × 60 ÷ 1,600 = 13.13 mL/h. The × 60 turns minutes into hours, and the concentration turns micrograms into millilitres of solution.
How do I get the concentration in mcg/mL?
Multiply the mg of drug by 1,000 to get mcg, then divide by the total volume in mL. 400 mg in 250 mL is 400 × 1,000 ÷ 250 = 1,600 mcg/mL. The calculator does this step for you and shows it first in the working, so you can check it against the infusion label.
How do I check what dose a running pump is giving?
Switch “I want to find” to “Dose (mcg/kg/min) from a pump rate” and enter the current mL/h. The formula is mL/h × mcg/mL ÷ (kg × 60). With 1,600 mcg/mL, 80 kg and 15 mL/h, the pump is giving 5 mcg/kg/min. It is a quick check at handover.
Why multiply by 60?
Because the dose is per minute and the pump runs per hour. Multiplying by 60 turns mcg per minute into mcg per hour before you divide by the concentration. Forget it and the rate comes out sixty times too low, which is one of the classic errors with these infusions.
What does “Drug delivered per hour” show?
It shows the total amount of drug the patient receives each hour, in mg: mcg/kg/min × kg × 60 ÷ 1,000. For 5 mcg/kg/min in a 70 kg patient that is 21 mg per hour. It is a useful cross-check against the amount in the bag and how long it will last.
Is gamma the same as mcg?
Yes. Gamma (γ) is an old name for the microgram, still heard in some units: 5 gamma/kg/min means 5 mcg/kg/min. It is safer to write mcg in orders and charts. Symbols like γ and µg are easy to misread, and a mix-up with mg means a thousand-fold error.
Which weight should I use?
It’s best to use the weight named in the prescription or local protocol. Some protocols use actual weight, others ideal or adjusted weight, and the rate changes in direct proportion. A 100 kg patient dosed on 70 kg ideal weight gets a rate 30% lower. It also helps to write down which weight you used.
Can I use it for drugs prescribed in units or in mcg/min?
No. This calculator expects the drug amount in mg and a weight-based dose in mcg/kg/min. Doses that are not per kg, such as mcg/min, and drugs measured in units, such as insulin or heparin, need a different calculation. It’s worth checking the units on the prescription before you start.