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NUR 101 Dosage Calculations (Common Approx Conversions and Rounding Rules)

NUR 101 Fundamentals CCTC Fall 2011 Judy G Whitaker
STUDY
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Oral Medications: Scored Tablets
Calculate to the tenth and round to the nearest half tablet:
1.5 tablets = give 1 1/2 tablets
1.7 tablets = give 2 tablets
Oral Medications: ALL other oral pills
Calculate to the tenth and round to the whole number:
1.4 tablets = give 1 tablet
1.9 tablets = give 2 tablets
Oral Medications: When preparing ORAL LIQUIDS:
Calculate to the hundredth and round to the tenth:
2.32 mL = give 2.3 mL
2.36 mL = give 2.4 mL
Injections: When giving more than 1 mL:
calculate to the hundredth and round to the tenth:
1.26 mL = give 1.3 mL
1.38 mL = give 1.4 mL
Injections: When giving less than 1 mL:
calculate to the thousandth and round to the hundredth:
0.823 mL = give 0.82 mL
0.666 mL = give 0.67 mL
When working with fractions that have repeating decimal:
it is recommended that you leave the fraction intact while working through the problem:
1/6 = 0.16666 -- leave as 1/6 to calculate the problem
Body Weight:
Calculate to the hundredth and round to the tenth:
7.35 kg = 7.4 kg
Tube Feeding: When calculating calories:
calculate to the tenth and round to the whole number
Tube Feeding: When calculating mL/hr:
calculate to the hundredth and round to the tenth
IV Problems: When calculating drop factor:
calculate to the tenth and round to the whole number
IV Problems: When calculating mg/min, mcg/hr, units/mL, mL/hr:
calculate to the hundredth and round to the tenth
IV Problems: When calculating titration factor:
carry out to the thousandth and round off to the nearest hundredth.
Type of Medication: Scored Tablets:
round to 1/2 tablet
Type of Medication: Oral Pills:
round to whole tablet
Type of Medication: Oral Liquids:
round to the tenth
Type of Medication: Injections over 1 mL:
round to the tenth
Type of Medication: Injection less than 1 mL:
round to the hundredth
Body Weight:
round to the tenth
Calories:
round to the nearest whole number
Tube Feeding mL/hr
round to the nearest tenth
Drop factors
round to the whole number
mg/min, mcg/hr, units/mL, mL/hr
round to the tenth
Volume: Metric: 1 Liter
1L = 1 qt or 32 oz (apothecary) = 1 qt (household)
Volume: Metric:
500 mL = 1 pt or 16 oz (apothecary) = 1 pt (household)
Volume: Metric: 240 mL
240 mL = 8 oz (apothecary) = 1 glass or 1 measuring cup (household)
Volume: Metric: 180 mL
180 mL = 6 oz (apothecary) = 1 cup of coffee
Volume: Metric: 30 mL
30 mL = 1 oz or 8 dr (apothecary) = 2 T or 6 t (household)
Volume: Metric: 15 mL
15 mL = 0.5 oz or 4 dr (apothecary) = 1 T (household)
Volume: Metric: 4 - 5 mL
4 - 5 mL = 1 dr or 60 minims (apothecary) = 1 t (household)
Volume: Metric: 1 mL or 1 cc
1 mL or 1 cc = 15 (16) minims (apothecary) = 15 - 16 gtt (household)
Weight: Metric: 30 g
30 g = 1 oz (apothecary)
Weight: Metric: 15 g
15 g = 4 drams (apothecary)
Weight: Metric: 1 g or 1000 mg
1 g or 1000 mg = 15 (16) gr (apothecary)
Weight: Metric: 60 (65) mg
1 gr (apothecary)
Weight: Metric: 1 mg or 1000mcg
1 mg = .001 g
Other: Metric: 1 kg or 1000g
1 kg or 1000 g = 2.2 lbs (apothecary)
Other: Metric: 2.54 cm
2.54 cm = 1 in (household)
Temperature Conversion: Celsius to Fahrenheit
F = 9/5 C + 32 or (C x 1.8) +32 = F
Temperature Conversion: Fahrenheit to Celsius
C = 5/9 (F-32) or (F -32) / 1.8 = C
Conversions:
1 g = 1000 mg
1000 mcg = 1 mg
1 kg = 1000 g
Gram
The basic unit for weight (solid).
Liter
The basic unit for volume (liquid).
Meter
The basic unit for length.
Kilo
1000 - One thousand times.
Hecto
100 - One hundred times.
Deka
10 - Ten times.
Deci
0.1 - One tenth.
Centi
0.01 - One hundredth part of.
Milli
0.001 - One thousandth part of.
Micro
0.000001 - One millionth part of.
g
Gram.
mcg
Microgram.
mg
Milligram.
kg
Kilogram.
L
Liter.
dL
Deciliter.
mL
Milliliter.
1 Kilogram (kg)
1000 grams (g)
1 gram (g)
1000 milligrams (mg)
1 milligram (mg)
1000 micrograms (mcg)
1 liter (L)
1000 milliliters (mL)
1 milliliter (mL)
0.001 liter (L)
1 meter (m)
100 centimeters (cm) = 1000 mm
1 millimeter (mm)
0.001 meter (m) = 0.1 cm
1 ounce (oz)
30 mL
1 tablespoon (T or tbs)
15 mL
2 tablespoons (T or tbs)
1 ounce (oz)
1 teaspoon (t or tsp)
5 mL
1 cup (standard measuring cup)
240 mL (8 ounces)
1 pint (pt)
500 mL (16 ounces)
1 quart (qt)
1000 mL (32 ounces)
15 grains (gr)
1000 mg = 1 gram (g)
1 grain (gr)
60 mg
2.2 pound (lb)
1 kg (1000 g)
1 inch (in)
2.5 cm
A patient has been taking 0.5g tablets of
acetaminophen (Tylenol) P.O. for
postoperative pain after an inguinal hernia
repair. If the patient took a total of 1,500
mg in 72 hours, how many 0.5-g tablets
were taken?
0.5g: 1 tab :: 1.5g :

X tab= 3 tablets
The doctor's order reads glyburide 1.5 mg
3 tablets P.O. daily. What's the total dose
in milligrams?
X = 4.5 mg
Your patient is receiving 500 mg of cefaclor oral suspension. The lable reads cefaclor 250mg/5ml, and the bottle contains 100ml. How many milliliters of cefaclor should you give? ,
x X 250 mg = 5 ml X 500 mg

X= 10 ml
The doctor orders 0.125 mg of digoxin (Lanoxin) elixir for a patient developing heart failure and pulmonary edema. The bottle is labeled 0.05 mg/ml. How many milliliters should the nurse administer?
0.05 mgX xml = 0.125 mg X 1ml

x = 2.5 ml
Your patient needs 400 mg of erythromycin oral suspension. the label reads erythromycin 200 mg/ 5 ml. How many milliliters should you give?
x X 200mg = 5 ml X 400 mg

x= 10ml
The doctor orders 100 mg Dilantin oral suspension t.i.d. for your patient. The label reads Dilantin 125 mg/5ml. How many mililiters should you give?
100 mg X 5 ml = 125 mg X x

x= 4ml
A doctor orders 25 g of lactulose (Cephulac) for a patient entereing a prehapatic coma. The bottle is labeled 10 g/15ml. How many milliliters should the patient receive?
10 g X xml = 15 ml X 25g

X= 37.5
Your patients's order reads aspirin gr 10 P.O. daily, but the unit-dose package says aspirin 325 mg. How many tablets should you administer daily?
60 mg X 10 grains = x X 1 grain

x X 325 mg = 1 tablet X 600 mg

X= 1.846 all probably round to 2
A prescriptoin reads phenobarbital gr 1/4 take gr 1/2 t.i.d. P.O. daily. How many milligrams of phenobarbital should this patient receive?
60 mg X grain 1/4 = X x 1 grain

X x grain 1/4 = 15mg x 1/2

X= 30 mg
Your patient receives a prescription for 62.5 mcg of digoxin elixir P.O. daily. The elixir reads 0.05 mg/ml. How many milliliters of digoxin should you give?
X x 0.05 mg = 1 ml x 0.0625

X= 1.25
patient is to receive 0.25 mg of Synthroid. The medication is only available in tablets that contain 125mcg each. How many tablet should the nurse administer?
X = 2 tablets
The doctor orders 0.05 mg Synthroid P.O., but the only Synthroid on hand is in tablets that contain 0.025 mg each. How many tablets should you give?
1 tablet X 0.05mg = 0.05 mg X x x=

2 tablets
1 liter (L) = ____ ml
1000 milliliters (ml)
1 ounce (oz) = ____ ml
30 milliliters (ml)
1 ounce (oz) = ____ tbsp
2 tablespoons (tbsp)
1 milliliter (ml) = ____ cc
1 cubic centimeter (cc)
1 teaspoon (tsp) = ____ ml
5 milliliters (ml)
1 tablespoon (tbsp) = ____ ml
15 milliliters (ml)
1 tablespoon (tbsp) = ____ tsp
3 teaspoons (tsp)
1 gram (g) = ____ mg
1000 milligrams (mg)
1 pint = ____ mg
500 milligrams (mg)
1 milligram (mg) = ____ mcg
1000 micrograms (mcg)
1 kilogram (kg) = ____ g
1000 grams (g)
1 kilogram (kg) = ____ lb
2.2 pounds (lb)
1 inch (in) (") = ____ cm
2.5 centimeters (cm)
8 ounces (oz) = ____ c
1 cup (c)
8 ounces (oz) = ____ ml
240 milliliters (ml)
grains (gr) X = ____ mg
650 milligrams (mg)
grains (gr) V = ____ mg
325 milligrams (mg)
240 milliliters (ml) = ___ c
1 cup (c)
65 milligrams (mg) = ___ gr
Grains (gr) 1
1 dram = ____ ml
4 milliliters (ml)
1 coffee cup = ____ oz
6 ounces
1 cup = ____ oz
8 ounces
1 quart = ____ L
1 liter
1 quart = ____ pints
2 pints
1 centimeter = ____ mm
10 millimeters
1 glass = ____ oz
12 ounces
Convert Celsius to Fahrenheit
1. multiply by 1.8
2. add 32
Convert Fahrenheit to Celcius
1. subtract 32
2. divide by 1.8