Drip Rate Calculator

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, as estimated in the dosage calculator. For example, imagine that you know that your patient needs 1 mg of a particular substance every minute. If you know the concentration (check the solution dilution calculator), 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).

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.

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.