Drip Rate Formula

The nurse is responsible for maintaining the proper flow rate while assuring the comfort and safety of the patient. The physician prescribes the flow rate. He indicates the amount of solution to be infused within a specified period of time. The rate is then determined on the basis of drops of solution to be infused every minute. This is called the DRIP RATE.

The drop factor, or drops per milliliter of solution is determined by the size of the opening in the infusion apparatus. It varies with the company producing the product. Most health agencies use the products of a single company. The most common drop factor are 10, 15, 20, and 60 drops per milliliter. Sixty drops milliliter is used most often when small fluid volumes are important such as with infants and small children. Adapters are also available that may be added to common infusion tubings to reduce the size of the drops.

A method for determining flow rate for an intravenous infusion is given below:

Legend:

gtts - drops
min - minute
hr - hour
ml - milliliter

To get the amount to infuse each hour

Formula:

The formula to get the amount to infuse each hour is vol / time (hrs) or volume of the solution to be given divided by the time (in hours) it would take for the solution to complete.

Example:

A physician prescribes 1000 ml of solution to be infused in a 10-hour period. Using the above formula, determine the amount to infuse each hour as follows:

In the example, we have 1000 ml / 10 hours, this gives us 100 ml of solution to be infused each hour.

To get the amount to infuse each minute

Formula:

The drip rate formula of getting the amount to infuse each minute is ml per hr x gtts per ml / time (mins) or the amount of the solution given in an hour multiplied by the drop factor and divided by the time it would take to complete the solution in minutes.

Example:

The drop factor is 15 gtts/ml and the amount of solution to be infused each hour is 100 ml. Using the above drip rate formula, determine the number of drops to infuse each minute as follows:

In our example, we have 100 ml x 15 gtts/ml / 60 mins. This gives us 25 gtts/min.

To get the number of mins/hrs to complete an infusion

Formula:

The formula to get the time it would take to complete the infusion is vol / gtts per min x gtts/ml or the total amount of solution to be given divided by the number of drops to infuse per minute, multiplied by the drop factor.

Example:

You have 500 ml of solution with a drip rate of 20 gtts/min, and calibrated with a  drop factor of 15 gtts/ml. Using the above formula, determine the number of hours it will take for the infusion to run out as follows:

The example shows 500 ml / 20 gtts/min x 15 gtts/ml, giving us 375 mins.

Now you got the number of minutes it will take for the infusion to complete. To get the number of hours:

The formula to convert minutes into hours is total mins / 60. That's because in one hour, there is 60 minutes. In our example, we have 375 mins / 60 min/hr, giving us 6.25 hrs.

Tools

Also check out our IV Drip Rate Calculator, it would make solving IV Drip Rate equations faster.