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IV Flow Rate Calculator

Calculate an infusion's flow rate in mL per hour from the volume and time, or the time to infuse, or the volume delivered, as educational arithmetic with checks.

Formula

rate (mL/h)=V (mL)t (h)\text{rate}\,(\mathrm{mL/h}) = \dfrac{V\,(\mathrm{mL})}{t\,(\mathrm{h})}
t (h)=V (mL)rate (mL/h)t\,(\mathrm{h}) = \dfrac{V\,(\mathrm{mL})}{\text{rate}\,(\mathrm{mL/h})}
V (mL)=rate (mL/h)×t (h)V\,(\mathrm{mL}) = \text{rate}\,(\mathrm{mL/h})\times t\,(\mathrm{h})
rate\text{rate}
flow rate, in mL per hour
VV
volume to be infused
tt
time over which it is given

How it works

The flow rate of an infusion is the volume divided by the time. Any two of the three quantities give the third. Volume and time can be entered in the units the order uses, and are converted to millilitres and hours.

This is the arithmetic a pump is programmed from. It says nothing about whether the rate is appropriate for the patient or the drug, which is decided by the order and the clinician, and every calculated rate should be checked against the order and independently verified before use.

Worked example

1,000 mL is to be given over 8 hours.

  1. Rate = 1,000 mL / 8 h = 125 mL/h.
  2. That is 125 / 60 = 2.08 mL/min.

The flow rate is 125 mL per hour.

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

Assumptions

  • A constant rate over the whole period.
  • The volume is the volume to be infused, not the bag size if they differ.

Common mistakes

  • Entering minutes where hours are expected. Use the unit selector.
  • Forgetting volume that is also delivered by flushes or by other lines.
  • Not checking the answer against the order, or not having it independently checked.

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Related equipment

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