The Dosage Calculation Workbook
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1. How Many Pills should I give?
Disclaimer: There are several valid ways that the nurse can use to calculate medication dosages.
These include ratio and proportion, dimensional analysis, and the formula method which is used
in this tutorial. The formula method is a modified way to use ratio and proportion. If you feel
more comfortable using any method, continue to use that method! All that really matters is that
the nurse accurately calculates the medication dosage.
Calculating the number of tablets or capsules to administer to a patient is one of the most common
calculations that a nurse is required to make. Read the tutorial, and then complete these 20 questions.
They will assist you in learning the principles of calculating tablet dosages.
How to calculate tablet dosages :
This formula is used to calculate the number of tablets to be administered when given the required dose:
Required Dose (D)
---------------------------- x (Q) = Number of tablets to be given
On Hand Dose (H)
Example 1:
A client is ordered 150 mg of aspirin. 300 mg aspirin tablets are available. How many tablets would
you give?
(D) 150 mg
------------------ X (Q) 1 tablet = 1/2 tablet
(H) 300 mg
Example 2:
How many tablets containing 62.5 mcg will be required to give a dose of 0.125 mg?
*STEP 1 : CONVERT TO SAME UNITS
Convert 0.125 mg to mcg.
The decimal place is moved 3 places to the right.
Mg - - kg hg dag g dg cg mg > > µg
0.125 mg = (0.125 * 1000 mcg)
= 125 mcg
*STEP 2: CALCULATE
(D) 125 mcg
------------------ X (Q) 1 tablet = 2 tablets
(H) 62.5 mcg
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OR…(see next page…)
STEP 1 : CONVERT TO SAME UNITS
Convert 62.5 mcg to mg.
The decimal place is moved 3 places to the left.
Mg - - kg hg dag g dg cg mg < < µg
62.5 mcg = (62.5 * 0.001 mg)
= 0.0625 mg
STEP 2: CALCULATE
(D) 0.125 mg
---------------------x (Q) 1 tablet = 2 tablets
(H) 0.0625 mg
PRACTICE QUESTIONS: (Answers are in the Dosage Calculation Workplace Appendix, separate
document)
1. A client is ordered 50 milligrams of Elavil. 25 milligram tablets are available. How many tablets
will you give?
2. A client is ordered 37.5 milligrams of Dothiepin. 75 milligram tablets are available. How many
tablets will you give?
3. A client is ordered 37.5 milligrams of Nortriptyline. 25 milligram tablets are available. How many
tablets will you give?
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4. A client is ordered 300 milligrams of Thioridazine. 100 milligram tablets are available. How many
tablets will you give?
5. A client is ordered 0.5 milligrams of Digoxin. 250 microgram tablets are available. How many
tablets will you give?
6. A client is ordered 1 milligram of Diazepam. 2 milligram tablets are available. How many tablets
will you give?
7. A client is ordered 300 milligrams of Carbamazepine. 200 milligram tablets are available. How
many tablets will you give?
8. A client is ordered 200 milligrams of Sodium Valproate. 100 milligram tablets are available. How
many tablets will you give?
9. A client is ordered 100 milligrams of Thioridazine. 25 milligram tablets are available. How many
tablets will you give?
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10. A client is ordered 7.5 milligrams of Bendrofluazide. 2.5 milligram tablets are available. How
many tablets will you give?
11. A client is ordered 100 milligrams of Pehthidine HCL. 50 milligram tablets are available. How
many tablets will you give?
12. A client is ordered 30 milligrams of Codeine phosphate. 60 milligram tablets are available. How
many tablets will you give?
13. A client is ordered 2.5 grams of Neomycin sulfate. 500 milligram tablets are available. How
many tablets will you give?
14. A client is ordered 30 milligrams of Diltiazem hydrochloride. 60 milligram tablets are available.
How many tablets will you give?
15. A client is ordered 62.5 micrograms of Benztropine Mesylate. 0.25 mg tablets are available.
How many tablets will you give?
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16. A client is ordered 60 milligrams of Phenelzine. 15 milligram tablets are available. How many
tablets will you give?
17. A client is ordered 37.5 milligrams of Clomipramine. 25 milligram tablets are available. How
many tablets will you give?
18. A client is ordered 1.25 milligrams of Clonazepam. 0.5 milligram tablets are available. How
many tablets will you give?
19. A client is ordered 2.5 milligrams of Haloperidol. 5 milligram tablets are available. How many
tablets will you give?
20. A client is ordered 40 milligrams of Imipramine. 10 milligram tablets are available. How many
tablets will you give?
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2. How much liquid medication should I give?
Calculating the volume of medication to administer to a patient is another one of the most common
calculations that a nurse is required to make. Read the tutorial, and then complete these 20 questions.
They will assist you in learning the principles of calculating tablet dosages.
How to calculate liquid / fluid dosages :
This formula is used to calculate the volume of liquid to be administered when given the required dose is
calculated slightly differently. The (Q) or volume per on hand medication is very important in the
equation:
Required Dose (D)
---------------------------- x Quantity of liquid per on hand medication (Q) = Volume of Liquid to be administered
On Hand Dose (H)
Example 1:
A client is ordered 150 mg of neomycin. Available dosage is 300 mg per 5 mL of liquid medication.
How much liquid medication would you give?
(D) 150 mg
------------------ X (Q) 5 mL = 2.5 mL
(H) 300 mg
Example 2:
How much liquid medication is required when the on hand medication is 62.5 mcg per 3 mL and
the ordered dose is 0.125 mg?
STEP 1 : CONVERT TO SAME UNITS
Convert 0.125 mg to mcg.
The decimal place is moved 3 places to the right.
Mg - - kg hg dag g dg cg mg > > µg
0.125 mg = (0.125 * 1000 mcg)
= 125 mcg
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STEP 2: CALCULATE
(D) 125 mcg
------------------ X (Q) 3 mL = 6 mL
(H) 62.5 mcg
OR…
STEP 1 : CONVERT TO SAME UNITS
Convert 62.5 mcg to mg.
The decimal place is moved 3 places to the left.
Mg - - kg hg dag g dg cg mg < < µg
62.5 mcg = (62.5 * 0.001 mg)
= 0.0625 mg
STEP 2: CALCULATE
(D) 0.125 mg
---------------------x (Q) 3 mL = 6 mL
(H) 0.0625 mg
PRACTICE QUESTIONS: (Answers are in the Dosage Calculation Workplace Appendix, separate
document)
1. A client is ordered 35 milligrams of Codeine phosphate by subcutaneous injection. 50
milligrams in 1 milliliter of liquid for SC Injection is available. How many milliliters will you
administer?
2. A client is ordered 50 milligrams of Amoxicillin trihydrate orally. 125 milligrams in 5 milliliters of
Syrup is available. How many milliliters will you administer?
3. A client is ordered 30 milligrams of Furosemide intravenously. 10 milligrams in 1 milliliter of
liquid for IV Injection is available. How many milliliters will you administer?
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4. A client is ordered 20 milligrams of Haloperidol decanoate by intramuscular injection. 50
milligrams in 1 milliliter of liquid for IM Injection is available. How many milliliters will you
administer?
5. A client is ordered 50 milligrams of Aminophylline intravenously. 250 milligrams in 10 milliliters
of liquid for IV Injection is available. How many milliliters will you administer?
6. A client is ordered 75 milligrams of Pethidine HCL by subcutaneous injection. 50 milligrams in 1
milliliter of liquid for SC Injection is available. How many milliliters will you administer?
7. A client is ordered 25 milligrams of Methyldopa intravenously. 50 milligrams in 5 milliliters of
liquid for IV Injection is available. How many milliliters will you administer?
8. A client is ordered 5 milligrams of Fluopenthixiol decanoate by intramuscular injection. 40
milligrams in 2 milliliters of liquid for IM Injection is available. How many milliliters will you
administer?
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9. A client is ordered 75 milligrams of Aminophylline intravenously. 250 milligrams in 10 milliliters
of liquid for IV Injection is available. How many milliliters will you administer?
10.A client is ordered 200 milligrams of Augmentin 600 intravenously. 600 milligrams in 6 milliliters of
liquid for IV Injection is available. How many milliliters will you administer?
11. A client is ordered 5 milligrams of Haloperidol orally. 2 milligrams in 1 milliliter of Syrup is
available. How many milliliters will you administer?
12. A client is ordered 13 milligrams of Morphine sulfate by intramuscular injection. 5 milligrams
in 1 milliliter of liquid for IM Injection is available. How many milliliters will you administer?
13. A client is ordered 22 milligrams of Gentamicin sulfate by intramuscular injection. 20
milligrams in 2 milliliters of liquid for IM Injection is available. How many milliliters will you
administer?
14. A client is ordered 75 micrograms of Fentanyl citrate intravenously. 0.1 milligrams in 1 milliliter
of liquid for IV Injection is available. How many milliliters will you administer?
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15. A client is ordered 50 milligrams of Sodium Valproate orally. 200 milligrams in 5 milliliters of
Syrup is available. How many milliliters will you administer?
16. A client is ordered 10 milligrams of Thioridazine orally. 50 milligrams in 5 milliliters of
suspension is available. How many milliliters will you administer?
17. A client is ordered 60 milligrams of Nefopam hydrochloride by intramuscular injection. 20
milligrams in 1 milliliter of liquid for IM Injection is available. How many milliliters will you
administer?
18. A client is ordered 200 milligrams of Amoxicillin trihydrate orally. 250 milligrams in 5 milliliters
of Syrup is available. How many milliliters will you administer?
19. A client is ordered 4 milligrams of Trifluoperazine orally. 5 milligrams in 5 milliliters of liquid
forte is available. How many milliliters will you administer?
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20. A client is ordered 2.5 milligrams of Promethazine hydrochloride orally. 5 milligrams in 5
milliliters of elixir is available. How many milliliters will you administer?
3. How much medication should I give, based upon the patient’s
weight?
Finding the units per kilogram adds a new dimension to previous dosage calculation problems.
Instead of the basic order, the provider will order a certain number of units (e.g., gram, milligrams,
micrograms) of the drug to be administered based on the patients weight, almost always given in
kilograms. This is referred to as an order based on patient’s weight. Look at the following example.
Example
**The Provider orders 5 mg/kg of Bretylium IV to be administered to your patient.
You have premixed syringes with 500 mg/10ml.
Your patient weights 176 lb.
How many milliliters will you administer?
First Things First! Convert lb to kg and then apply kg to the basic order to obtain the Desired Dose.
Now, organize the other key components in the order.
Desired Dose: 400 mg (176 lb ÷ 2.2 = 80 kg 80 X 5 mg = 400
Concentration: 500 mg
Volume on Hand: 10 ml
Lbs to Kg: 176 lb = 80 kg
mg, this is the Desired Dose)
So the desired dose is 400 mg.
Now we are looking for: how many ml to be given.
This is a liquid dose calculation:
(D) 400 mg
X (Q) 10 mL = 8 mL
------------------
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(H) 500 mg
PRACTICE QUESTIONS: (Answers are in the Dosage Calculation Workplace Appendix, separate
document)
1. A client is ordered Mangastrine 5 mg/kg IM, for one dose only. On hand you have Mangastrine
250 mg/ mL. The patient’s weight is 75 kg. How many milliliters will you administer?
2. A client is ordered 5 milligrams / kg of Amoxicillin trihydrate orally. Patient’s weight is 125 lbs.
125 milligrams in 5 milliliters of Syrup is available. How many milliliters will you administer?
3. A client is ordered 0.5 milligrams / kg of Furosemide intravenously. Patient’s weight is 198 lbs.
10 milligrams in 1 milliliter of liquid for IV Injection is available. How many milliliters will you
administer?
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4. A client is ordered 0.2 milligrams per kg of Haloperidol decanoate by intramuscular injection.
50 milligrams in 1 milliliter of liquid for IM Injection is available. Patient’s weight is 110 lbs. How
many milliliters will you administer?
5. A client is ordered 5 milligrams per kg of Aminophylline intravenously. Patient’s weight is 158
lbs. 250 milligrams in 10 milliliters of liquid for IV Injection is available. How many milliliters will
you administer?
4. How do I calculate IV Flow Rates?
How to calculate IV flow rates :
Intravenous fluid must be given at a specific rate, neither too fast nor too slow. The specific rate
may be measured as ml/hour, L/hour or drops/min. To control or adjust the flow rate manually
(without an IV Pump) only drops per minute are used.
The burette or drip chamber in IV tubing contains a needle or plastic dropper which gives the
number of drops per ml (the drop factor).
A number of different drop factors are available (determined by the length and diameter of the IV
tubing drip set up / design).
Common drop factors are:
10 drops/ml (blood set),
15 drops / ml (regular set),
60 drops / ml (micro drop).
To measure the rate we must know:
(a) the number of drops
(b) time in minutes.
One formula for working out flow rates is:
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volume (ml) X drop factor (drops/ml)
---------------------------------------------= drops / minute
time (min)
Example:
1500 ml IV Saline is ordered over 12 hours. Using a drop factor of 15 drops / ml, how many drops
per minute need to be delivered?
1500 (ml) X 15 (drops/ml)
---------------------------------------------- = 31 drops / minute
12 x 60 (gives us total minutes)
*Another formula, a modified dimensional analysis method is as follows:
Volume ordered mL
time
1 hour___
60 minutes
_15 gtt______ = # __?__ _gtt__
1 mL
minute
This is the “Drop
Factor” -variable with
the type IV
Tubing Used
Example:
IV Saline is ordered at a rate of 120 mL per hour. Using a drop factor of 15 drops / ml, how many
drops per minute need to be delivered?
120 mL
hour
1 hour___
60 minutes
_15 gtt______ = 1800 = 30 _gtt__
1 mL
60
minute
See succeeding pages for practice problems.
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PRACTICE QUESTIONS: (Answers are in the Dosage Calculation Workplace Appendix, separate
document)
1. Calculate the drip rate for 100 mLs of IV Fluids to be given over a half hour via a giving set
which delivers 10 drops/ml.
2. One liter of Normal Saline is charted over 9 hours. The drop factor is 15. Calculate the number
of drops per minute.
3. One and a half liters of Normal Saline is required to be given over 4 hours. Using a giving set
which delivers 10 drops/ml how many drops per minute will need to be given?
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4. Calculate the drip rate for 2 liters of IV Fluids to be given over 5 hours via a giving set which
delivers 10 drops/ml.
5. Ordered: 1 liter of Dextrose 5% in water over 8 hours using a giving set which delivers 10
drops/ml. Calculate the rate in drops/minute.
6. You are required to administer 100 mLs of IV Fluids over 1 hour. The drop factor is 15. How
many drops per minute are required to start the flow off at the correct rate?
7. You are required to administer 500 mLs of Normal Saline over 3.5 hours. The drop factor is 10.
How many drops per minute are required to start the flow off at the correct rate?
8.Calculate the drip rate for 500 mLs of Normal Saline to be given over 4.5 hours via a giving set
which delivers 15 drops/ml.
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9. You are required to administer 1 liter of Normal Saline over 7 hours. The drop factor is 10. How
many drops per minute are required to start the flow off at the correct rate?
10. One liter of Dextrose 5% in water is charted over 8 hours. The drop factor is 10. Calculate the
number of drops per minute.
11. You are required to administer 3 liters of IV Fluids over 12 hours. The drop factor is 10. How
many drops per minute are required to start the flow off at the correct rate?
12. Calculate the drip rate for 500 mLs of Dextrose 5% in water to be given over 4 hours via a
giving set which delivers 15 drops/ml.
13. One and a half liters of IV Fluids is prescribed over 8 hours. The drop factor is 15. How many
drops per minute are required to start the flow off at the correct rate?
14. Three liters of Lactated Ringer's IV fluid is charted over 12 hours. The drop factor is 15. The IV
has been running for 9 hours. 800 mLs remain. How many drops per minute are needed so that
the IV finishes in the required time?
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15. Calculate the drip rate for 100 mLs of IV Fluids to be given over 2 hours via a giving set which
delivers 60 drops/ml.
16. One liter of Dextrose 5% in water is charted over 3 hours. The drop factor is 10. The IV has
been running for 1 hour and 15 minutes. 500 mLs remain. How many drops per minute are needed
so that the IV finishes in the required time?
17. You are required to administer 1 liter of Normal Saline over 7 hours. The drop factor is 15. How
many drops per minute are required to start the flow off at the correct rate?
18. One liter of IV Fluids is charted over 11 hours. The drop factor is 10. The IV has been running
for 9 hours and 45 minutes. 100 mLs remain. How many drops per minute are needed so that the
IV finishes in the required time?
19. Three liters of Normal Saline is charted over 12 hours. The drop factor is 15. The IV has been
running for 9 hours and 45 minutes. 500 mLs remain. How many drops per minute are needed so
that the IV finishes in the required time?
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20. One hundred milliliters of IV Fluids is charted over 2.5 hours. The drop factor is 15. Calculate
the number of drops per minute.
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