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Drops Per Minute Calculator

Michelle Saari MSc, RD

Fact Checked And Reviewed By Adrian White, Certified Herbalist

By Michelle Saari MSc, RD, Registered Dietitian

Last Updated on April 11th, 2024

Estimates the intravenous rate at which different fluids should be administered in accordance to a prescription.
Refer to the text below the tool for more information about determining the IV drops per minute.

Purpose

Depending on the volume to be administered, the duration and the established drop factor of an intravenous fluid prescription, the drops per minute rate must be calculated.

Formula

IV Drip rate (Drops per minute) = (Volume to be given in mL x Drop factor in gtts/mL) / Time in minutes

Calculating the drops per minute needed for an intravenous (IV) administration, then our drops per minute calculator can help make this calculation simple for you.

Ensuring that a patient receives the right amount of volume is important for managing their IV fluids and medications.  

What is Drops per Minute?

When administering an IV you may know the overall volume that a patient will be receiving, but you need to also calculate how many drops per minute.  Most machines that administer IVs will require this number.  

There are a few things that you need to know before this calculation.  Here are the top 3 items to know:

  1. The total volume that will be in the IV fluid mixture.  This is usually expressed as millimetres (mL).
  2. Length of time the IV will be administered.  This will vary, it may be anywhere from minutes to hours of administration time.
  3. The drop factor is also important, it needs to be determined what the macrodrip tubing will be.  This is usually expressed in gtts/mL.  

Drops per Minute formula

If we look at what the formula would be when putting all of these factors together we get:

Drops per Minute Rate = (Total volume in mL x Drop Factor in gtts/min) / Total time administered (in minutes)

This will give you the drops per minute rate, or the rate at which the IV will be administered in minutes.  

Let’s illustrate this with an example

If the total volume is 500 mL, the administration time is 60 minutes, and the drop factor is 15 gtts/mL, the drops per minute would be:

Drops per Minute = (500 mL × 15 gtts/mL) / 60 minutes = 125 drops per minute

Common Drops per Minutes and Tubing Types

Most intravenous (IVs) therapies will have one of the most common rates that are observed in clinical settings:

  • 10 gtts/mL
  • 15 gtts/mL
  • 20 gtts/mL
  • 60 gtts/mL

60 gtts/mL is more often used when a microdrip tubing is used for an IV, because it is a much thinner tube and has a higher drip factor.  Microdrips are used for more precision administration, and macrodrips are used more often for blood transfusions.

The rate however will be patient dependent on their overall health and medical conditions.  All drops per minute rates should be confirmed by either a Doctor or Nurse that is working with the patient.

What is the PEACE Method?

Administering an IV is a serious job as many will administer medications, cancer therapies, essential fluids, blood transfusions, and other rehydration therapies.  

Many healthcare professionals will use what we call the PEACE method to ensure that they don’t forget any steps when starting an IV.  Here is what the acronym stands for.

PEACE LettersRepresentsMeaning
PPlanPlan exactly what medication or fluids will be needed, and what the exact dosage is.
EEstimateSome will estimate the needs before doing their final calculations.
AApproachAsk yourself what, how, when, and where for all phases of administering an IV.
CCalculateComplete the exact calculations needed for administering the IV.
EEvaluateHave another healthcare professional double check all of your calculations for the IV administration before hooking it up.

Anyone administering an IV should always use a drops per minute calculator and should have another colleague check their work for the safety of their patients.  

FAQs on IV Drip Rate Calculations and Drops Per Minute Calculator

How do I calculate drops per minute if I know the volume and time of the infusion?

To calculate the drops per minute, use the formula:
Drops per Minute = (Total Volume × Drop Factor) / Total Time
For example, if the total volume is 500 mL, the infusion time is 60 minutes, and the drop factor is 15 gtts/mL, the calculation would be:
Drops per Minute = (500 mL × 15 gtts/mL) / 60 minutes = 125 drops per minute

How do I convert the drip rate from mL/hour to drops per minute?

To convert the drip rate from mL/hour to drops per minute, you can use the following formula:
Drops per Minute = (Drip Rate in mL/hour × Drop Factor) / 60
For example, if the drip rate is 100 mL/hour and the drop factor is 20 gtts/mL, the calculation would be:
Drops per Minute = (100 mL/hour × 20 gtts/mL) / 60 = 33.33 drops per minute

What is the difference between macrodrip and microdrip tubing?

Macrodrip tubing typically has a lower drop factor, ranging from 10 to 20 gtts/mL. This type of tubing is commonly used for less critical infusions, such as blood transfusions.

Microdrip tubing has a higher drop factor, usually around 60 gtts/mL. This type of tubing is used for more precise and controlled IV administrations, often in pediatric cases or for medications with a narrow therapeutic range.

The higher the drop factor, the slower the infusion rate will be for a given volume and time.

How can I ensure accurate drip rate control?

To ensure accurate drip rate control, follow these steps:

Count the number of drops in the drip chamber for one minute.
Use the roller clamp to adjust the drip rate as needed.
Count the drops again to verify the desired drip rate.

Some IV administration devices may have electronic flow control mechanisms that calculate the drip rate for you. However, it’s still a good practice to double-check the results.

Why is precise control of the drip rate important?

Precise control of the drip rate is crucial to patient safety. Even seemingly harmless solutions, such as saline, can have potentially serious side effects if administered at the wrong rate. Infusion rates that are too fast can lead to complications like encephalopathy, seizures, and paralysis.

It’s especially important to carefully monitor and adjust the drip rate when treating conditions like hyponatremia, where the correction rate should not exceed 6-12 mEq/L in the first 24 hours and 18 mEq/L or less over 48 hours.

References

https://www.nursingcenter.com/ncblog/december-2021/how-to-calculate-drops-per-minute

Michelle Saari MSc, RD

Written By

Michelle Saari MSc, RD

Registered Dietitian

Michelle Saari is a Registered Dietitian based in Canada. She has a Master's Degree in Human Nutritional Sciences and is a passionate advocate for spreading easy to understand, reliable, and trustworthy nutrition information. She is currently a full-time blogger with two elderly nutrition-focused health blogs.