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

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NUR 101 Fundamentals CCTC Fall 2011 Judy G Whitaker

### 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)

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

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.

10 - Ten times.

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.

Gram.

Microgram.

Milligram.

Kilogram.

Liter.

Deciliter.

Milliliter.

1000 grams (g)

### 1 gram (g)

1000 milligrams (mg)

### 1 milligram (mg)

1000 micrograms (mcg)

### 1 liter (L)

1000 milliliters (mL)

0.001 liter (L)

### 1 meter (m)

100 centimeters (cm) = 1000 mm

### 1 millimeter (mm)

0.001 meter (m) = 0.1 cm

30 mL

15 mL

1 ounce (oz)

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)

60 mg

1 kg (1000 g)

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

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

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)

1000 grams (g)

2.2 pounds (lb)

### 1 inch (in) (") = ____ cm

2.5 centimeters (cm)

1 cup (c)

### 8 ounces (oz) = ____ ml

240 milliliters (ml)

### grains (gr) X = ____ mg

650 milligrams (mg)

### grains (gr) V = ____ mg

325 milligrams (mg)

1 cup (c)

Grains (gr) 1

### 1 dram = ____ ml

4 milliliters (ml)

6 ounces

8 ounces

1 liter

2 pints

10 millimeters

12 ounces

### Convert Celsius to Fahrenheit

1. multiply by 1.8

1. subtract 32
2. divide by 1.8

Example: