Drip Rate Calculator

Created by Bogna Szyk and Aleksandra Zając, MD
Reviewed by Steven Wooding
Last updated: Jul 31, 2022

This drip rate calculator will help you determine the rate of applying a liquid drug in intravenous therapy. You can use this IV drip calculator to find the drip rate in ml/min or the flow rate in gtts/min (drops per minute).

If you are not sure what values you should provide as the input, keep reading for a step-by-step explanation of how to calculate the drip rate. We will also provide you with a drip rate formula, which you can use for manual calculations.

We try our best to make our Omni Calculators as precise and reliable as possible. However, this tool can never replace a professional doctor's assessment. If any health condition bothers you, consult a physician.

What is the IV drip rate?

In an IV (intravenous) therapy, the drip rate is defined as the rate of application of a liquid drug required to provide a specific dosage per minute. For example, imagine that you know that your patient needs 1 mg of a particular substance every minute. If you know the solution concentration, you can easily calculate how many ml of the drug you should provide every minute.

The flow rate is very similar to the drip rate. The only difference between the two is their units – flow rate is measured in gtts/min (drops per minute).

Flow rate and drip rate formulas

We calculate the drip rate according to the following formula:

Drip rate = (60 × Desired dose / 1000 × Weight × Bag volume) / (1000 × Drug in bag)

where:

  • Desired dose – Dosage of the drug, expressed in milligrams per kilogram of body weight per minute;
  • Weight – Weight of the patient, measured in kilograms;
  • Bag volume – Total volume of one bag of the liquid medicine, expressed in milliliters; and
  • Drug in bag – Mass of the medicine in the drug solution, measured in milligrams.

Once you know the drip rate, you can easily convert it to flow rate. All you need to do is to use the following equation:

Flow rate = Drip rate × Drop factor

where:

  • Drop factor – Number of drops (gtts) per milliliter of the liquid substance.

How to calculate the drip rate: an example

  1. Determine the desired dose of the drug. Let's assume you need to provide 0.02 mg/kg/min.

  2. Measure the patient's weight – let's say that in this case, it is equal to 85 kg.

  3. Choose the drug solution. Let's say you provide bags of 10 mg of the drug dissolved in 40 ml of water.

  4. Use the first equation to calculate the drip rate:

    Drip rate = (60 × Desired dose / 1000 × Weight × Bag volume) / (1000 × Drug in bag)

    Drip rate = (60 × 0.02 / 1000 × 85 × 40) / (1000 × 10) = 408 ml/h

    You need to set the drip rate at 408 ml/h.

  5. Let's assume that the drop factor is equal to 10 drops per milliliters. To find the flow rate, use the second formula:

    Flow rate = Drip rate × Drop factor

    Flow rate = 408 ml/h × 10 gtts/ml = 4080 gtts/h = 68 gtts/min

    You have to set the flow rate at 68 gtts/min.

Bogna Szyk and Aleksandra Zając, MD
Desired dose
mg/
lb
/min
Body weight
lb
Concentration
mg/L
Bag volume
ml
Drug in bag
mg
Drip rate
ml
/h
Drop factor
gtts/
ml
Flow rate
gtts/
per minute
Time to end bag
hrs
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