Conversion is the first step in dosage calculations for medication administration, as medications may not always be prescribed in the same unit. Memorizing the conversions will help you with dosage calculations and administration. For temperature, 0° Celsius is equivalent to 32° Fahrenheit. To convert Celsius to Fahrenheit, multiply Celsius by 1.8 and then add 32. To convert Fahrenheit to Celsius, minus 32 and divide by 1.8. 

To convert Celsius to Fahrenheit, multiply Celsius by 1.8 and then add 32. F = 1.8 x C + 32. 

To convert Fahrenheit to Celsius, minus 32 and divide by 1.8. 

Weight 

• One thousand micrograms (mcg) is equivalent to 1 milligram (mg). To convert micrograms to milligrams, multiply the number of milligrams by 1000. 
• One thousand milligrams (mg) is equivalent to 1 gram (g). To convert grams to milligrams, multiply the number of grams by 1000. 
• One thousand grams (g) is equivalent to 1 kilogram (kg). To convert kilograms to grams, multiply the number of kilograms by 1000. 
• One kilogram (kg) is equivalent to 2.2 pounds (lbs). To convert from kilograms to pounds, multiply the number of kilograms by 2.2.

Volume

• One milliliter (mL) is equivalent to 1 cc (cubic centimeter).
• Five milliliters (mL) is equivalent to 1 teaspoon (tsp). To convert teaspoons to milliliters, multiply the number of teaspoons by 5. 
• Fifteen milliliters (mL) is equivalent to 1 tablespoons (tbsp). To convert tablespoons to milliliters, multiply the number of tablespoons by 15. 
• Thirty milliliters (mL) is equivalent to 1 fluid ounce (oz). To convert ounces to milliliters, multiply the number of ounces by 30. 
• One thousand milliliters (mL) is equivalent to 1 liter (L). To convert liters to milliliters, multiply the number of liters by 1000. 
• Two tablespoons (tbsp) equivalent to 1 fluid ounce (oz). To convert fluid ounces to tablespoons, multiply the number of ounces by 2. 
• Eight fluid ounces (oz) is equivalent to 1 cup. To convert cups to ounces, multiply the number of cups by 8.

Formulas 

Desired / Have x Vehicle

Desired = What do you WANT to give the patient? (This is what the HCP ordered, what the prescription is for, etc.)

Have= This is the quantity of medication (mgs, mcgs, grams…) that you actually have on hand. What the label says on the bottle, what the pharmacy sent up, etc.

Vehicle= This is what that medication you have in you hand actually comes in.

You can’t see the mgs, mcgs, etc…. You CAN see the ml’s, tablets, capsules…. This is what you will actually be able to measure out for your patient.

(D/H) x V 

Example:

You receive an order to administer 400 mg ibuprofen to your patient PRN q6 hours. You retrieve the medication, which comes in 200 mg tablets. How many tablets do you administer to your patient?

Desired = 400 mg ibuprofen

Have = 200 mg tablets

Vehicle = 1 tablet

(400 mg / 200 mg) x 1 tablet = 2 tablets

Drip Factors

As a general rule, IV infusions are administered using an IV pump that runs in mL/hr. However, you will be asked questions regarding drip rates and drip factors. Use this equation:

Drip rate: (Order x Drip Factor) Time in Minutes  

Number of Milliliters per Hour

Calculation of these problems can be done using a two-step process.

1. Determine the amount of medication per milliliter (mL).

2. Determine the infusion rate or milliliters per hour.

Volume / Time in hours  = Milliliters per Hour

You can obtain our Pharmacology Manual HERE