IV Flow Rate Calculator

By Dominika Miszewska, PhD candidate
Last updated: Nov 25, 2021

This IV flow rate calculator (also an IV drip rate calculator) helps determine the correct drip rate of an intravenous fluid - based on the volume and time the medicine should be administered over that has been prescribed for the patient. You may have already noticed the abbreviation of intravenous into IV.

As administering medication comes with a big responsibility, we aim to make IV calculations easier. In the article below, you can find some information regarding the IV flow rate formula and how to put the IV flow rate estimations in practice. Also, take a look at our drip rate calculator, which helps you get through the whole process of intravenous drug preparation.

What is the IV flow rate?

The first thing you should know is that the flow rate formula is sometimes called the drip rate formula. Have you ever wondered why and how to calculate the IV flow rate? There are two options:

  1. If you're in the hospital, you can use macrodrip or microdrip tubing without an electronic pump. Therefore, the IV flow rate is defined as the number of drops of medication a patient receives over a determined time (e.g., drops per minute). One drop is quite a small amount and cannot be divided into smaller parts - so the values for IV flow rate in this calculator are rounded to the digits column.

  2. You can use an electronic infusion controller (infusion pump). In this case, the IV flow rate should be defined as the volume divided by the time of infusion - e.g., milliliters per minute or US fluid ounces per minute.

IV flow rate formula

To use the IV drip rate formula for infusions without a pump, you need to know:

  • Drop factor.
  • Total volume of the solution - you should know that there are some drugs which have to be diluted in, e.g., saline solution or glucose.
  • Time over which the patient should receive the drug.

So, what is drop factor? It is the number of drops it takes to make up one ml of fluid.

There are two common sizes for drop factor:

  • 15 drops (ggts) per ml (for fluids with a density significantly greater than water, e.g., blood).
  • 20 drops (ggts) per ml (for fluids with a density similar to water, e.g., most drugs dissolved in saline).

However, in our IV flow rate calculator, you can set your own drop factor. Once you know all the values, you can use the IV flow rate formula:

Flow rate (in drops) = Drop factor * Volume / Time

As mentioned above, this IV flow rate calculator also counts the IV flow rate in milliliters per minute at the same time:

Flow rate = Volume / Time

You might find it useful when using electronic infusion controllers.

How to calculate the IV flow rate?

Let's go through a quick example. Let's take a patient, who needs to receive 500 ml of intravenous saline solution, with a drop rate of 20 drops/ml. The whole infusion should last around 2 hours.

What is the drip rate?

20 ggts/ml * 500 ml / 120 min = 83 ggts/min

The correct flow rate is around 83 drops per minute.

If the nurse needed the flow rate in milliliters per minute, she could make use of the second line:

500 ml / 120 min = 4.17 ml/min

IV drip rate calculations

Giving the patient the right medication in the correct dose is a big responsibility. On the one hand, the doctor has to prescribe the proper dosage. On the other, nurses have take care of its administration, double-checking the right prescriptions is being administered, any recalculations, and determining the IV drip rate.
The first thing that needs to be done is to review the patient's data: their age, body mass, and the amount of medication prescribed.

Administration of drugs in tablet form is easier since you either divide one tablet into parts or give a certain amount of tablets. However, when intravenous medication is considered, there are a couple of different types:

  • Single-dose vial
  • Multiple-dose vial
  • Prefilled syringe containing a patient-specific dose
  • Drug to dilute

Thankfully, now you know how to calculate the IV flow rate!

Remember that if you are a pediatrician, the dosages of medication your patient needs to receive may differ. Check out our paracetamol calculator or ibuprofen calculator) for the relevant formulas.

Once you have everything, always look carefully at the units of your calculations. In our IV flow rate calculator, you can switch between different volume units and times of administration. Remember to check it before counting!

Dominika Miszewska, PhD candidate
Drop factor
Total volume
US fl oz
Infusion time
Fluid rate results
IV flow rate (in drops)
IV flow rate
UK fl oz / min
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