D
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CALCULATIONS
TERMS & CONCEPTS
What is the IV flow rate?
The speed at which
intravenous fluid infuses
into the body
What are the tubing sizes?
10, 15, or 20 gtt/mL
(Macrodrip tubing)
60 gtt/mL (Microdrip tubing)
What is the drop factor?
The number of drops
(abbreviated “gtt”)
required to deliver 1mL
of fluid
What determines gtt/mL?
The size of the IV
administration set
(tubing)
How do you calculate the IV flow rate?
Using the IV flow rate formula
IV FLOW RATE FORMULA
IV Flow Rate Formula is used when calculating an infusion
by gravity (without an IV pump).
Volume to be Infused (in mL) x Drop Factor = Flow Rate
Total Infusion Time (in minutes)
(in gtt/min)
Electronic Flow Rate Formula is used when calculating an
infusion by IV pump (electronic infusion device, or EID).
Volume to be Infused (in mL) = Flow Rate
Total Infusion Time (in hours)
(in mL/h)
*Round all rates to the nearest whole number
DOSAGE CALCULATIONS
Complete necessary conversions (i.e. dosage per
weight, mass, volume, etc) prior to using either of the
two previous flow rate formulas.
Conversions may be calculated using:
Ratio/Proportion
Dimensional Analysis
Whatever method you are most comfortable with and use
consistently/correctly
!
Order: Infuse 800mL of NS in 10 hours.
#1
• This is a straight-forward IV flow rate
calculation, in which no conversion is required.
• We know we will be using the Electronic Flow
Rate Formula because we were not given the
tubing size or drop factor, which would be
required to calculate a gravity flow rate.
• The correct formula is:
800mL ÷ 10 hours =
80mL/h
Volume to be Infused (in mL) = Flow Rate
Total Infusion Time (in hours)
(in mL/h)
Order: Infuse 150mL of D5W in 30 minutes using an
#2
administration set with a drop factor of 20gtt/mL.
• This is also a straight-forward IV flow rate
calculation, in which no conversion is required.
• We know we will be using the IV Flow Rate
Formula because we were given the drop factor.
• The correct formula is:
150mL x 20gtt/mL ÷ 30
minutes = 100gtt/min
Volume to be Infused (in mL) x Drop Factor = Flow Rate
Total Infusion Time (in minutes)
(in gtt/min)
Order: Infuse 100mL of LR by IV pump in 20
minutes.
#3
• We know we will be using the Electronic Flow Rate
Formula because we were directed to use an IV
pump, and because we were not given the tubing
size or drop factor.
• Before using our flow rate formula, we must
complete the necessary conversion(s).
• To use our Electronic Flow Rate Formula, we need the total volume to be infused in mL (which
we know), and the total infusion time in hours (which we don’t know).
• We must convert minutes to hours using our chosen dosage calculation method.
CONTINUED
Order: Infuse 100mL of LR by IV pump in 20 minutes.
Our calculation method of choice is ratio/proportion,
which involves a 3-part process: 1) Set up ratio, 2)
Cross-multiply, 3) Isolate X by dividing its value by
itself
Step 1
20 min = X hour
60 min 1hour
Step 2
60(X) = 20(1) or 60X = 20
Step 3
60X = 20 so X = 0.33
60 60
CONTINUED
Order: Infuse 100mL of LR by IV pump in 20
minutes.
Now that we have converted minutes to hours (20
minutes = 0.33 hours), we can use our
Electronic Flow Rate Formula to solve our IV
dosage calculation problem.
100mL ÷ 0.33 hours = 303mL/h
(The IV pump would be programmed for 303 mL
per hour in order to infuse the desired 100 mL in
20 minutes.)
Order: Infuse 200mL of D5W in 4 hours using a
Microdrip tubing.
• We know we will be using the IV Flow Rate
Formula because we were given a tubing size
(remember that a Microdrip administration set
#4
delivers 60gtt/mL).
• Before using our flow rate formula, we must
complete the necessary conversion(s).
• To use our IV Flow Rate Formula, we need the total volume to be infused in mL (which we know),
the drop factor (which we also know), and the total infusion time in hours (which we don’t know).
• We must convert hours to minutes using our chosen dosage calculation method.
CONTINUED
Order: Infuse 200mL of D5W in 4 hours using a
Microdrip tubing.
Complete the conversion calculation.
Step 1
4 hours = X minutes
1 hour 60 minutes
Step 2
1(X) = 4(60) or 1X = 240
Step 3
1X = 240 so X = 240
1
1
CONTINUED
Order: Infuse 200mL of D5W in 4 hours using a
Microdrip tubing.
Now that we have converted hours to minutes (4
hours = 240 minutes), we can use our IV Flow
Rate Formula to solve our IV dosage calculation
problem.
200mL x 60gtt/mL ÷ 240 minutes = 50gtt/min
(The roller clamp on the IV tubing would be
manually regulated to deliver 50 drops per
minute.)
REMINDERS
When preparing to tackle any type of IV flow rate
calculation, be sure to determine what, if any,
conversions need to take place first.
Once you have completed all necessary conversions, you
are ready to calculate the IV flow rate using one of the
two IV flow rate formulas we’ve discussed in this
tutorial.
Remember, it is always best to be consistent with the
dosage calculation method you choose to use when
completing this type of problem.
Order: Give 500mg of dopamine in 250mL of D5W to infuse at
20mg/h. Calculate the flow rate in mL/h.
*In order to know how many mL we need to infuse in 1 hour per
the IV pump, we need to convert our dosage needed (20mg)
into its equivalence in mL.
*Set up ratio, and then cross-multiply:
500mg = 250mL
so
500X = 250(20)
20mg
X mL
*Isolate X and solve:
500X = 5000
500
500
so
X = 10mL
*There are 20mg of dopamine in 10mL of solution, so we will
program our IV pump at 10mL/h.
Your patient has an order to receive 800U of heparin per hour by
continuous intravenous infusion. If the pharmacy mixes the IV
bag to contain a total of 5,000U of heparin in 500mL of D5W,
how many mL per hour should the patient receive?
*In order to calculate mL/hour, we need to convert our dosage
needed (800U) into its equivalence in mL.
*Set up ratio, and then cross-multiply:
5000U = 500mL
so
5000X = 500(800)
800U
X mL
*Isolate X and solve:
5000X = 400,000
5000
5000
so
X = 80mL
*There are 800U of heparin in 80mL of solution, so we will
program our IV pump at 80mL/h.
Order: 21.7mg of dopamine in 105mL of D5W to be infused at a
rate of 9mg/h. Calculate the flow rate in mL/h.
*In order to calculate mL/hour, we need to convert our dosage
needed (9mg) into its equivalence in mL.
*Set up ratio, and then cross-multiply:
21.7mg = 105mL
9mg
so
21.7X = 9(105)
X mL
*Isolate X and solve:
21.7X = 945
21.7
so
X = 43.55mL
21.7
*There are 9mg of dopamine in 43.55mL of solution, so we will
program our IV pump at 44mL/h.
Order: Aggrastat at 12.5mg in 250mL to be infused at a rate of 6
mcg/kg/hr in a patient who weighs 100kg. At what flow rate will you
set the IV pump?
*For problems that include a weight/mass, do that conversion 1 st:
6mcg per kg = 6mcg x 100kg = 600mcg/hr
*Since our ordered dose is in mg, we need to convert mcg to mg:
600mcg ÷ 1000 = 0.6mg/hr
*In order to calculate mL/hour, we need to convert our dosage needed
(0.6mg) into its equivalence in mL.
*Set up ratio, and then cross-multiply:
12.5mg = 250mL
0.6mg
so
12.5X = 0.6(250)
X mL
*Isolate X and solve:
12.5X = 150
12.5
so
X = 12mL
12.5
*There are 0.6mg of Aggrastat in 12mL of solution, so we will program
our IV pump at 12mL/h.
A 1000cc solution of D5NS with 20,000U of heparin is infusing at
20mL/h. The IV set delivers 60gtt/mL. How many units of
heparin is the patient receiving each hour?
*This is a reverse calculation, as we already know the electronic
flow rate (mL/h). We will use our dosage calculation method to
work through the problem.
*Set up ratio, and then cross-multiply:
20,000U = 1000mL so
1000X = 20(20,000)
XU
20mL
*Isolate X and solve:
1000X = 400,000
so
X = 400U
1000
1000
*There are 400U of heparin in 20mL of solution, which means
the patient is receiving 400U of heparin per hour. The drop
factor is simply a distracter, and is not used in this problem.
The physician orders an IV infusion of D5W 1000mL to be
infused over the next 8 hours. The IV tubing you are using
delivers 15gtt/mL. What is the correct rate of flow?
*In order to use the IV Flow Rate Formula, we need to know time
in minutes instead of hours, which is the only conversion we
will need to do to solve this problem.
*We can eliminate the extra steps of a time conversion by
incorporating it into our formula:
1000mL x 15gtt/mL = 15,000 = 31.25
8 h x 60 min
480
*Remember our “mL” labels are cancelled out during the
calculation process, and we must round all flow rates, leaving
us with 31gtt/min as the correct rate of flow.
Your patient has an order to infuse 10mEq of KCl in 100mL of
D5½NS over the next 30 minutes. The set calibration is
10gtt/mL. What is the correct rate of flow?
*We will be using the IV Flow Rate Formula, and no conversion
calculation is needed:
100mL x 10gtt/mL = 1000 ÷ 30 = 33.33
30 min
*The correct rate of flow is 33gtt/min.
*Do not be confused by extra numbers, such as are used in the
name of a solution (i.e. D5W or ½NS). These have no bearing
on your dosage calculation.
*Be careful in determining which value(s) are pertinent in solving
your problem. In this example, the 10mEq of KCl is not a
necessary component in terms of calculating the correct rate
of flow, so ignore it!
The 0900 medications scheduled for your patient include Keflex
1.5g in 50mL of a 5% dextrose solution. According to the
pharmacy, this preparation should be administered in 30
minutes. The IV tubing on your unit delivers 15gtt/mL. What is
the correct rate of flow in gtt/min?
*We will be using the IV Flow Rate Formula, and no conversion
calculation is needed:
50mL x 15gtt/mL = 750 ÷ 30 = 25
30 min
*The correct rate of flow is 25gtt/min.
*Again, remember the 5% dextrose is just describing the type of
solution, and the Keflex 1.5g does not have anything to do with
calculating the flow rate for this problem.
On Wednesday afternoon, your patient returns from surgery with
an IV fluid order for 1000mL every 8 hours. On Thursday
morning at 0800, you note that 600mL of a 1L bag has been
infused. The physician orders the remainder of the bag to
infuse over the next 6 hours. The IV tubing used by your unit
delivers 10gtt/mL. What is the correct rate of flow?
*There are 400mL remaining in the IV bag, which needs to be
infused in 6 hours.
*We need to know time in minutes instead of hours, which can
be incorporated into our IV Flow Rate Formula calculation:
400mL x 10gtt/mL = 4000 ÷ 360 = 11.11
6 h x 60 min
*The correct rate of flow is 11gtt/min.
The physician orders 1.5L of Lactated Ringers solution to be
administered intravenously to your patient over the next 12
hours. Calculate the rate of flow if the IV tubing delivers
20gtt/mL.
*In order to utilize the IV Flow Rate Formula, we must convert
liters to milliliters and hours to minutes, both of which can be
completed as part of the formula calculation:
(1.5L x 1000) x 20gtt/mL = 30,000 ÷ 720 = 41.67
12 h x 60 min
*The correct rate of flow is 42gtt/min.
Miscellaneous
Dosage
#1: The physician orders 200mg of Rocephin to be
taken by a 15.4 lb infant every 8
hours. The
medication label shows that 75-150 mg/kg/day is
the appropriate dosage range for this medication. Is
the order within the desired range?
Convert weight (lbs to kg):
15.4 lbs ÷ 2.2 = 7kg
Calculate minimum and maximum dosage:
75mg x 7kg = 525mg
(minimum daily therapeutic dose)
150mg x 7kg = 1050mg
(maximum daily therapeutic dose)
Determine if the order is within range:
200mg every 8 hours (or 200mg x 3 times
per day) = 600mg
Solve the problem:
Yes, 600mg/day of Rocephin is within the
desired daily range of 525mg and 1050mg for
this patient.
#2: Solumedrol 1.5mg/kg is ordered for a
child
weighing 34 kg. This medication is available as
125mg/2mL. How many mL will you administer?
Calculate mg according to weight:
1.5mg/kg x 34 kg = 51mg
Convert mg to mL using your chosen dosage
calculation method:
125mg = 2mL so 125X = 51(2)
51 mg X mL
125X = 102 so X = .82mL
125 125
Solve the problem:
You will administer 0.82mL of Solumedrol to
this patient.
#3:
You are to infuse 800mL of Lactated
Ringers over 20 hours using an IV
administration set that delivers 20gtt/mL. What
is the drip rate?
Solve using the IV Flow Rate Formula:
800mL x 20gtt/mL = 16,000gtt = 13gtt/min
20 h x 60 min
1200 min
Calculate the mL/h of the following orders via IV
pump:
#4.
Administer 1500mL of 0.9 NS in 24 hours.
#5.
Administer 750mL of LR in 16 hours.
#6.
Administer 500mL of D5W in 12 hours.
#7.
Administer 2000mL of D5W in 24 hours.
Solve the previous calculations using the Electronic
Flow Rate Formula:
1500mL ÷ 24 hours = 63mL/h
750mL ÷ 16 hours = 47mL/h
500mL ÷ 12 hours = 42mL/h
2000mL ÷ 24 hours = 83mL/h
#8
Order: Administer 30mL of Ancef in 0.9 NS
over 20 minutes via intravenous infusion
pump.
Convert minutes to hours:
20 minutes = X hours so 60X = 20(1)
60 minutes 1 hour
60X = 20 so X = 0.33∞ hours
60
60
Solve using the Electronic Flow Rate Formula:
30mL ÷ 0.33∞ hours = 90mL/h
#9
Order: Administer 100mL of ½NS in 45
minutes.
Convert minutes to hours:
45 minutes = X hours so 60X = 45(1)
60 minutes 1 hour
60X = 45 so X = 0.75 hours
60
60
Solve using the Electronic Flow Rate Formula:
100mL ÷ 0.75 hours = 133mL/h
#10 Order: Administer 150mL of D5W in 30
minutes.
Convert minutes to hours:
30 minutes = X hours so 60X = 30(1)
60 minutes 1 hour
60X = 30 so X = 0.5 hours
60
60
Solve using the Electronic Flow Rate Formula:
150mL ÷ 0.5 hours = 300mL/h
#11 Your patient is to receive 2000mL of D5W with
a flow rate of 160mL/h. How long will
this order
take to infuse?
Solve using your chosen dosage calculation formula:
2000mL = X hours so 160X = 2000(1)
160mL
1 hour
160X = 2000 so X = 12.5 hours
160
160
*It will take 12 ½ hours to infuse 2000mL of D5W to
your patient under this order.
#12 Your patient has been prescribed 1L of NS.
The IV pump is set at 150mL/h. How long will
this order take to infuse?
Solve using your chosen dosage calculation formula:
1L x 1000 = 1000mL
1000mL = X hours so 150X = 1000(1)
150mL 1 hour
150X = 1000 so X = 6.7 hours
150
150
*It will take just under 7 hours to infuse 1000mL of
NS to your patient under this order.
#13 The physician orders D5W IV at 125mL/h. The
infusion set is calibrated for a drop factor of
10gtt/mL. Calculate the IV flow
rate in gtt/min.
Solve using the IV Flow Rate Formula:
125mL x 10gtt/mL = 1250gtt = 21gtt/min
1 h x 60 min
60 min
#14 Order: 150mL Lactated Ringers solution to
infuse in 30 minutes. The drop factor is
15gtt/mL.
Solve using the IV Flow Rate Formula:
150mL x 15gtt/mL = 75gtt/min
30 min
#15 Order: Cefazolin 0.5g in 100mL D5W IV
piggyback to run over 30 minutes. The
factor is 20gtt/mL. What is the drip rate?
drop
Solve using the IV Flow Rate Formula:
100mL x 20gtt/mL = 67gtt/min
30 min
#16 Order: Ampicillan 500mg IV in 100mL of NS to
infuse over 45 minutes. How will you
program
the infusion pump?
Convert minutes to hours:
45 minutes = X hours so 60X = 45(1)
60 minutes 1 hour
60X = 45 so X = 0.75 hours
60
60
Solve using the Electronic Flow Rate Formula:
100mL ÷ 0.75 hours = 133mL/h
#17 Order: Bactrim 500mg IV in 50mL D5½NS
in 30 minutes by IV pump. What is the
mL/h?
Convert minutes to hours:
30 minutes = X hours so 60X = 30(1)
60 minutes 1 hour
60X = 30 so X = 0.5 hours
60
60
Solve using the Electronic Flow Rate Formula:
50mL ÷ 0.5 hours = 100mL/h
#18 Order: NS 1800mL IV to infuse in 15 hours
by infusion pump. Calculate the flow rate.
Solve using the Electronic Flow Rate Formula:
1800mL ÷ 15 hours = 120mL/h
#19 You receive a physician’s order for D5W
250mL IV over the next 2 hours by infusion
pump. What is the mL/h?
Solve using the Electronic Flow Rate Formula:
250mL ÷ 2 hours = 125mL/h
#20 You receive an order for D5W 500mL with
heparin 25,000U IV at 850U per hour.
Calculate the flow rate in mL/h.
Convert U/h to mL/h to solve this problem:
25,000U = 500mL so 25,000X = 850(500)
850U
X mL
25,000X = 425,000 so X = 17mL/h
25,000
25,000
*The flow rate is 17mL/h.
#21 You receive an order for D5W 1000mL IV to
infuse at 50mL/h to begin at 0600. At
what time
will this IV be complete?
Solve using your chosen dosage calculation formula:
1000mL = X hours so 50X = 1000(1)
50mL
1 hour
50X = 1000 so X = 20 hours
50
50
*This IV will be complete at 0200 the following
morning.
#22 You receive an order for LR solution 1000mL IV
to run at 125mL/h. How long will
this IV last?
Solve using your chosen dosage calculation formula:
1000mL = X hours so 125X = 1000(1)
125mL
1 hour
125X = 1000 so X = 8 hours
125
125
*This IV will last for 8 hours.
#23 Order: Dobutamine 250mg in 250mL D5W
per IV to infuse at 5mcg/kg/min. The
client’s weight is 80 kg. Calculate the flow rate
using an infusion pump.
Calculate mcg according to weight:
5mcg/kg x 80 kg = 400mcg/min
Convert mcg/min to mg/min:
400mcg ÷ 1000 = 0.4mg/min
Convert mg/min to mg/hour:
0.4mg x 60 minutes = 24mg/h
Convert mg to mL based on dosage on hand:
250mg = 250mL so 250X = 24(250)
24mg
X mL
250X = 6000 so X = 24mL
250
250
Solve using the Electronic Flow Rate Formula:
24mL/h via IV pump
#24 Order: Lidocaine 2g in 500mL D5W IV to run
at 4 mg/min. What is the flow rate per
IV pump?
Convert g to mg:
2g x 1000 = 2000mg
Convert mg/min to mL/min based on dosage on hand:
2000mg = 500mL so 2000X = 4(500)
4mg
X mL
2000X = 2000 so X = 1mL/min
2000 2000
Convert mL/min to mL/h to solve the problem:
1mL x 60 minutes = 60mL/h
#25 Order: Ancef 1g in 100mL D5W IV piggyback
to be infused over 45 minutes.
You are using a
Microdrip tubing. What is
the flow rate in gtt/min?
Solve using the IV Flow Rate Formula:
100mL x 60gtt/mL = 133gtt/min
45 min
#26 Order: 50mL Zofran solution IV piggyback to
infuse over 30 minutes. The drop factor is
60gtt/mL. What is the flow rate in gtt/min?
Solve using the IV Flow Rate Formula:
50mL x 60gtt/mL = 100gtt/min
30 min
#27 Order: 1000mL D5W IV q 24 hours. The drop
factor is 60gtt/mL. What is the flow rate in gtt/min?
Convert hours to minutes and solve using the IV Flow
Rate Formula:
1000mL x 60gtt/mL = 60,000 = 42gtt/min
24 hours x 60 minutes 1440
#28 A dose strength of gr ¼ of an IV push
medication is ordered. The available
dosage is 15mg/mL. How many mL will
administer?
you
Convert gr to mg:
1grain = 60mg so 1X = ¼(60)
¼ grain X mg
1X = 15 so X = 15mg
1
1
Solve the problem:
15mg = 1mL, so you will administer 1mL.
#29 You have an order for epinephrine to be
infused at 30mL/h. The solution available is
2mg of epinephrine in 250mL D5W. Calculate the
mcg/min.
Convert mL/h to mg/h based on dosage on hand:
2mg = 250mL so 250X = 2(30)
X mg 30mL
250X = 60 so X = 0.24mg/h
250 250
Convert mg/h to mcg/h:
0.24mg x 1000 = 240mcg/h
Convert mcg/h to mcg/min to solve the problem:
240mcg ÷ 60 minutes = 4mcg/min
#30 Aminophyline 0.25g is added to 500mL
to infuse in 8 hours. Calculate the mg/h.
D5W
Use the Electronic Flow Rate Formula to determine
mL/h:
500mL ÷ 8h = 62.5mL/h
Convert mL/h to g/h based on dosage on hand:
0.25g = 500mL so 500X = 0.25(62.5)
Xg
62.5mL
500X = 15.6 so X = 0.03g/h
500 500
Convert g/h to mg/h to solve the problem:
0.03g x 1000 = 30mg/h
#31 You receive an order to infuse 500mL ½NS
with 30,000U heparin at 600U/h. The drop
factor is 60gtt/mL. What is the gtt/min?
Convert U/h to mL/h per on dosage on hand:
30,000U = 500mL so 30,000X = 500(600)
600U
X mL
30,000X = 300,000 so X = 10mL/h
30,000
30,000
Convert hours to minutes and solve using the IV Flow
Rate Formula:
10mL x 60gtt/mL = 10gtt/min
1 hour x 60 minutes
#32 A patient is to receive Pitocin at
15microgtt/min. The solution contains 10U
Pitocin in 1000mL D5W. Calculate the
number of units of Pitocin the patient is
receiving per hour.
Convert mgtt/min to mgtt/h:
15mgtt x 60 minutes = 900mgtt/h
Convert mgtt/h to mL/h (*remember Microdrip tubing
delivers 60 drops in 1mL):
60mgtt = 1mL so 60X = 900(1)
900mgtt X mL
60X = 900
60
60
so X = 15mL/h
*Continued on next slide
Convert mL/h to U/h:
10U = 1000mL
XU
15mL
so
1000X = 10(15)
1000X = 150 so X = 0.15U
1000 1000
Solve the problem:
The patient is receiving 0.15U/hour of
Pitocin.
#33 You have an order for 3 mcg/kg/min of
Nipride. You have available 50mg of Nipride in
250mL D5W. The client’s weight is 60 kg. Calculate
the flow rate in mL/h that will deliver the correct dose.
Calculate mcg according to weight:
3mcg/kg x 60 kg = 180mcg/min
Convert mcg/min to mg/min:
180mcg ÷ 1000 = 0.18mg/min
Convert mg/min to mg/hour:
0.18mg x 60 minutes = 10.8mg/h
Convert mg to mL based on dosage on hand:
50mg = 250mL so 50X = 10.8(250)
10.8mg X mL
50X = 2700 so X = 54mL
50
50
Solve using the Electronic Flow Rate Formula:
54mL/h via IV pump
#34 A 50mg nitroglycerin drip in 250mL D5W is
infusing at 3mL/h. Calculate the mcg/min of
nitroglycerin this patient is receiving.
Convert mL/h to mg/h based on dosage on hand:
50mg = 250mL so 250X = 50(3)
X mg
3mL
250X = 150 so X = 0.6mg/h
250 250
Convert mg/h to mcg/h:
0.6mg x 1000 = 600mcg/h
Convert mcg/h to mcg/min to solve the problem:
600mcg ÷ 60 minutes = 10mcg/min
#35 A dose strength of 0.3g of a medication has
been ordered to infuse over 20
minutes. The
available dosage is 0.4g in
1.5mL of solution.
Calculate the mL/h.
Convert g to mL based on dosage on hand:
0.4g = 1.5mL so 0.4X = 0.3(1.5)
0.3g
X mL
0.4X = 0.45 so X = 1.125mL
0.4
0.4
Convert minutes to hours:
20 minutes = X hours so 60X = 20(1)
60 minutes 1 hour
60X = 20 so X = 0.33∞ hours
60 60
Use the Electronic Flow Rate Formula to solve:
1.125mL ÷ 0.33∞ hours = 3mL/h