IV Rate Calculations
Rule of thumb: set up the algebraic equation so you get the desired units for the answer, and the other units cancel each
other out. For example, with “how many drops per minute,” the “ml” unit cancels out of the equation to leave
gtts/min.
How many drops per minute?
Formula:
??ml
X ??gtts = gtts
60 min
ml
min
Example: using an IV drip chamber with a drop factor of 15 gtts/ml, to infuse 125 ml/hr, how many
gtts/min would you use to regulate the IV?
125ml
60 min
X 15 gtts = ~31 gtts/min
ml
The provider order will indicate the amount/hr or you may have to calculate the amount/hr if the order is
to administer, for example, one liter over 8 hrs.
Drip spouts (also called drop factors) have different gtts/ml based on the manufacturer so you need to
check the wrapping for the gtts/ml. Drip spouts may produce 15, 20, or 60 gtts/ml
How many ml per hour?
Formula:
?? ml in the IV bag
= ml
?? hrs ordered for the bag to infuse hr
Example: the provider orders a liter (=1000ml) of fluid over 8 hrs.
1000 ml in the IV bag
= 125 ml/hr
8 hrs ordered for the bag to infuse
How much fluid did the patient receive for a specified time period?
Formula:
??ml
X ?? hr = ml
hr
Example: A patient received 75ml/hr of a solution for 8 hrs. You have to calculate the intake for the 8 hr
period.
75 ml
X 8 hr = 600 ml
hr
How long with the infusion take?
Formula:
hr
X ??ml = hr
??ml
Example: The patient requires one unit (350ml) of PRBCs to be infused at 100 ml/hr. How long will the
infusion take?
hr
X
100ml
350ml = 3.5 hr