Drops per minutes (Intravenous Drips)
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| Course: | Part A Numeracy |
| Book: | Drops per minutes (Intravenous Drips) |
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| Date: | Sunday, 6 September 2026, 2:20 PM |
1. Drops per minutes
Intravenous Drips
(Drops per minutes)
To calculate the Flow Rate, this is simply the volume in ml divided by the duration in hours. Both these values will be prescribed.
Example: A patient requires 500ml IVI over twelve hours. What is the flow rate ?
Answer 500 divided by 12 is 41.66ml/hr . If you do not the facility to enter decimals then round to the nearest whole number. The answer would then be 42ml/hr.
This constant quantity gives rise to the "drop factor" which is the number of drops which make up every millilitre of fluid delivered. Two common sizes are 20 drops per ml and 15 drops per ml. A special paediatric infusion controller is available which delivers 60 drops per ml.
The Drop Rate is defined by below:
Drop rate = total drops
time in minutes
If the total volume of fluid is given in millilitres and the drop factor for the controller is known (usually 20drops/m1 or 15 drops/ml), the total number of drops which the patient will receive can be calculated by:
Total number of drops = drop factor X volume in ml
Also, if the time is given in hours, we can calculate the time in minutes from:
60 X time in hours
So the formula is:
Drop rate = drop factor X volume in ml
60 X time in hours
Example: 500ml of 5%dextrose solution is to be given intravenously. The infusion controller has a drop factor 20 drops per ml and you are instructed to ensure that the patient receives this volume in 12 hours. What should the drop rate be set to ?
Answer:
Drop rate = 20 drops per ml X 500ml = 13.89
60 X 12 hours
Note that it is necessary to round to the nearest whole number, because infusion controllers which are calibrated to operate in drops per minute do not have the facility for decimals, so the answer would be 14 drops per minute.